— ■ 


HX641 40687 


RC115.W73  Insects  and  disease,    J 


RECAP 


AMERICAN  MUSEUM  OF  NATURAL  HISTORY 


Insects  and  Disease 


BY 

C.-E.  A.  WINSLOW 

AND 

FRANK  E.  LUTZ 


GUIDE  LEAFLET  No.  48 


Columbia  Wlni\}tv$ity 
in  ifje  €itp  of  Jl^eto  g^orfe 

College  of  ipbpsictang  anb  Hmrgeoite 


Reference  Htbrarp 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

Open  Knowledge  Commons 


http://www.archive.org/details/insectsdiseasestOOwins 


INSECTS  AND  DISEASE 

A  Statement  of  the  More  Important 

Facts  with  Special  Reference  to 

Everyday  Experience 


BY 


C.-E.  A.  Winslow  and  Frank  E.  Lutz 


American  Museum  of  Natural  History 


GUIDE  LEAFLET  No.  48 

NEW  YORK,  JUNE,   191! 

PRINTED  AT  THE   MUSEUM 


"I  deal  with  certain  little  Invertebrata;  animals 
which  work  in  darkness  and  in  stealth,  little  animals 
which  in  times  of  Peace  we  politely  ignore,  yet 
little  animals  which  in  times  of  War  may  make  or 
unmake  an  army  corps.  As  that  wise  old  Greek, 
Aristotle,  wrote — and  he  knew  quite  a  lot  about 
them — 'One  should  not  be  childishly  contemp- 
tuous of  the  study  of  the  most  insignificant  animal. 
For  there  is  something  marvellous  in  all  natural 

objects.'  " 

A.  E.  Shipley,  " Minor  Horrors  of  War." 


INSECTS  AND  DISEASE 

By  C.-E.  A.  Winslow 

and  F.  E.  Lutz 


THE  IMPORTANCE  OF  INSECTS 

The  life  of  man  is  affected,  for  good  or  ill,  at  a  thousand  points 
by  the  activities  of  the  humbler  members  of  the  living  world  of  which 
he  forms  a  part.  The  lower  animals  and  plants  supply  us  with  our 
food  and  clothing  and  with  materials  for  providing  shelter  against 
the  elements.  On  the  other  hand,  certain  species  are  our  relentless 
foes,  waging  constant  war  against  our  property  and  even  our  lives. 

In  the  case  of  the  insects,  for  example,  as  we  review  the  multitudes 
of  these  creatures  within  our  limited  horizon,  we  not  only  admire  the 
wondrous  beauty  of  this  species  or  the  amazing  instincts  of  that;  we 
are  awestruck  at  the  financial  havoc  wrought  by  one  and  appre- 
ciate with  gratitude  the  way  in  which  another  helps  to  restore  the 
balance  of  Nature  and  protect  us  from  starvation.  Even  among  the 
microbic  forms  of  life,  in  the  world  of  the  "infinitely  little,"  we  find, 
on  the  one  hand,  the  bacteria  of  the  soil  fixing  the  nitrogen  of  the  air 
and  making  it  available  for  our  growing  Crops  —  on  the  other,  the 
bacilli  of  tuberculosis  and  of  a  score  of  other  deadly  diseases,  threaten- 
ing the  health  and  life  of  hundreds  of  thousands. 

One  of  the  most  interesting  and  important  chapters  in  the  story 
of  the  interrelationships  between  mankind  and  the  lower  forms  of 
life  is  that  which  deals  with  the  triple  relation  between  the  microbe, 
the  insect  and  the  human  being  in  the  spread  of  certain  communi- 
cable diseases.  The  types  of  insects  and  their  relatives  concerned 
are,  on  the  whole,  more  disgusting  than  beautiful;  their  habits  are  not 
attractive,  nor  are  their  instincts  extraordinary;  but  they  have  pro- 
foundly influenced  the  history  of  the  human  race^  You  and  I  may 
lose  our  lives  by  reason  of  their  activities;  we  certainly  can  aid  in 
combating  them .  It,  therefore,  behooves  us  to  become  well  acquainted 
with  our  foes. 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


CHARACTERISTICS  OF  INSECTS 

First  of  all,  a  word  should  be  said  as  to  the  characteristics  of  these 
creatures  and  their  place  in  Nature.  Those  animals  which  have  no 
internal  skeleton  but  do  have,  at  some  period  of  their  lives,  jointed 
legs  are  called  Arthropods.  Familiar  examples  are  lobsters,  spiders, 
centipedes,  and  insects.  We  are  now  chiefly  concerned  with  certain 
insects  but  we  must  also  consider  mites  and  ticks,  creatures  which  are 
more  closely  related  to  the  spiders.  An  insect  has  its  body  divided 
into  three  regions:  head,  thorax,  and  abdomen.  Its  jointed  legs  are 
borne  by  the  thorax,  the  segments  of  the  body  which  are  just  back  of, 
but  separated  from,  the  head;  there  are  never  more  than  three  pairs 
of  such  legs  in  an  adult  insect.  Spiders,  mites,  and  ticks  have,  typi- 
cally, four  pairs  of  jointed  legs,  and  the  head  is  merged  with  that  part 
of  the  body  which  bears  the  legs. 

The  great  majority  of  insects  are  winged,  when  adult,  and  most 
winged  insects  have  two  pairs  of  wings,  but  the  members  of  the  large 
Order  Diptera,  to  which  mosquitoes  and  flies  belong,  have  never 
more  than  one  pair.  Nearly  all  of  the  strictly  parasitic  insects  are 
wingless,  even  when  adult.  We  will  take  up  first  those  disease-bearing 
insects  which  have,  when  adult,  one  pair  of  wings,  next  certain 
wingless  insects,  and  finally  the  mites  and  ticks. 

Two  sorts  of  Diptera  or  two-winged  insects  are  of  interest  in  the 
present  connection:  (1)  ordinary  "flies"  with  three-jointed  antenna;; 
and  (2)  mosquitoes,  gnats,  etc.,  which  have  eight  or  more  freely 
moving  joints  in  each  antenna.  The  Muscida;  and  the  Tabanidse 
(p.  13)  are  of  the  first  sort. 

The  Muscidse,  a  group  which  includes  our  commonest  disease- 
bearing  insect,  the  filth  fly,  are  characterized  as  follows: 

The  squamse  (see  Fig.  1)  of  Diptera  are  scale-like  structures  placed 
back  of  the  roots  of  the  wings  and  above  the  knobbed  "balancers"; 
and  the  Muscida;  agree  with  the  related  Diptera  in  having  these 
squamse  large.  The  auxiliary  vein  in  the  wing  (see  Fig.  1)  is  distinct 
in  its  whole  course,  and  the  first  longitudinal  vein  is  never  very 
short.  The  thorax  has  a  complete  transverse  suture.  The  eyes  of 
the  male  are  usually  much  nearer  together  than  those  of  the  female; 
sometimes,  in  fact,  so  close  that  they  touch  each  other. 


INSECTS  AND  DISEASE 


Fig.  1.    THE  FILTH  FLY  (Musca  domestica) 


Auxiliary  vein 

/• 

Antennae 

First  longitudinal  vein 

</• 

Transverse  suture 

Fourth  longitudinal  vein 

h. 

Squama 

Discal  cell 

i. 

Abdomen 

Anal  cell 

j> 

Tibia 

THE  FILTH  FLY 

Musca  domestica 

More  volumes  have  been  written  about  this  insect  in  the  last 
twenty  years  than  have  been  devoted  to  any  other  one  insect  (unless 
it  be  the  honey-bee)  since  man  became  civilized  enough  to  write 
about  insect's  at  all. 

This  fly  is  commonly  called  the  "house  fly,"  but  that  name  has 
been  justly  criticized  because  it  seems  to  imply  a  necessary  domestic 
relation.  We  do  not  believe  that  this  insect  should  be  a  house  fly  in 
the  future;  and  Dr.  L.  O.  Howard  of  Washington,  in  view  of  its  re- 
lation to  disease,  has  suggested  that  is  should  be  called  the  Typhoid 
Fly.  This  seems,  on  the  other  hand,  to  relate  rather  too  closely 
a  disease  and  an  insect  which  are  sometimes,  but  not  universally, 
connected.  Filth  Fly  is  perhaps  the  best  term  and  one  that  is  un- 
doubtedly applicable.  The  fly  breeds  in  filth,  it  resorts  to  filth,  and 
it  carries  filth  with  it  everywhere  it  goes. 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

The  excellent  figures  given  here,  combined  with  common  experi- 
ence, are  sufficient  for  the  identification  of  the  "ordinary  house  fly," 
or  "typhoid  fly,"  or  "filth  fly."  Note  (Figs.  1  and  4)  especially  the 
rounded  angle  in  the  fourth  longitudinal  vein,  the  plumose  antennal 
bristle,  the  absence  of  stout  bristles  on  the  abdomen,  the  absence  of 
a  vertical  row  of  bristles  between  the  base  of  the  hind  legs  and  the 
"balancers,"  and  the  absence  of  a  prominent  bristle  near  the  middle 
of  either  middle  tibia.  As  is  the  case  with  many  other  Diptera,  the 
males  of  this  species  have  the  eyes  closer  together  than  do  the  females. 
The  sides  of  the  abdomen  in  the  male  are  brownish  near  the  base 
and  grayish  elsewhere.  The  females  are  grayish  over  the  whole 
abdomen  with  a  variable  pattern  of  darker  gray  or  black. 

The  filth  fly,  like  all  other  Diptera,  passes  through  four  definite 
stages  in  its  life  cycle:  egg,  larva,  pupa,  and  adult.  The  eggs  of  the 
fly  (one  or  two  hundred  in  number)  are  laid  by  preference  in  horse 
manure  but  may  also  be  deposited  in  almost  any  moist  decaying 
organic  matter,  such  as  "human  excrement,  pig  manure,  decaying 
grain,  moist  bran,  moist  mixtures  of  hay  and  grain  from  feed  troughs 
of  animals,  excreta-soiled  straw,  contents  from  slaughtered  animals, 
decaying  kitchen  refuse,  rotting  fruits  and  vegetables,  excreta-soiled 
paper  and  rags,  and  ensilage."  Dr.  Howard  estimates  that  probably 
90'f  of  our  filth  flies  are  hatched  from  horse  manure.  Only  certain 
portions  of  a  manure  pile  are,  however,  favorable  for  fly  breeding, 
"a  layer  some  inches  deep  and  lying  a  few  inches  below  the  surface 
where  there  may  be  found  a  moderate  amount  of  heat  and  moisture, 
an  excess  of  either  being  fatal  or  compelling  migration." 

It  takes  the  eggs  of  the  fly  about  twelve  hours,  on  the  average, 
to  hatch.  The  larva?  are  whitish  creatures,  blunt  at  the  posterior 
end  and  pointed  in  front.  They  have  no  bristles  or  hairs.  On  the 
blunt  end  are  spiracles  or  breathing  holes.  In  young  larva;  these 
spiracles  are  in  a  heart-shaped  aperture;  later  they  appear  in  two  slits; 
and  still  later  in  three  winding  slits.  The  changes  occur  when  the 
larva;  cast  their  skins  at  intervals  during  their  growth  while  feeding 
on  the  manure  or  other  material  in  which  they  live. 

About  five  days  after  hatching,  the  maggot,  now  about  half  an 
inch  long,  burrows  downward  into  the  ground  or  outward  into  the 
drier  portions  of  the  manure  and  there  changes  to  a  brownish  pupa 
about  %  inch  long.  The  pupal  stage  may  last  from  three  or  four 
days  to  several  weeks,  and  recent  observations  suggest  that  autumn 
broods  usually  pass  the  winter  in  this  form,  although  the  fly  may 


INSECTS  AND  DISEASE 


Fig.  2.     EGGS,  LARVA  AND  PUPA  OF  THE  FILTH  FLY 

(Photograph  of  models  in  The  American  Museum  of  Natural  History) 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

hibernate  in  any  stage.  At  the  termination  of  the  pupal  stage  the  fly 
comes  out  of  the  pupal  case  and  crawls  up  to  the  surface  of  the  ma- 
terial in  which  it  pupated.  Here  its  wings  quickly  harden  and  it  is 
ready  to  fly  away. 

The  rate  at  which  generations  of  flies  follow  each  other  is  deter- 
mined by  the  temperature.  Studies  made  in  the  Laboratory  of 
Public  Health  of  the  American  Museum  gave  a  total  period  from 
egg  laying  to  the  emergence  of  the  adult  of  9.3  days  at  35°  C,  10.3 
days  at  30°  C,  and  22.3  days  at  20°  C. 

The  adult  fly  lives  upon  liquid  food,  since  its  mouth  parts  are  in 
the  form  of  a  sucking  proboscis,  but  by  discharging  a  free  flow  of 
saliva  it  is  able  to  turn  foods  like  sugar  into  the  fluid  form  it  can 
absorb. 


Total  Period    9j30»rs  jrJ>\ 

^  .._        JL 


3SC 


THE  RELATION  OF  TEMPERATURE 

TO  THE 

LIFE  CYCLE  OF  THE  HOUSEFLY 


Total  Period    IO.SDays 


»       ■»       V     » 


Total  Period   2l.3Days 


THE 
Fig.  3 


INSECTS  AND  DISEASE 


Fig.  4.    THE  FILTH  FLY  (Musca  domestica) 

(Photograph  of  model  in  The  American  Museum  of  Natural  History) 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


RELATIVES  OF  THE  FILTH  FLY 
There  are  a  number  of  other  flies  sometimes  found  in  houses 
which  may  be  mistaken  for  the  Filth  Fly,  and  the  characteristics  of 
a  few  of  them  may  be  briefly  described. 

Homalomyia  canicularis  is  often  supposed  to  be  a  "young  house 
fly."  It  does  look  like  a  small  edition  of  the  more  common  and 
dangerous  insect;  but  it  is  a  wholly  different  species.  No  insect  grows 
after  it  has  attained  to  the  dignity  of  wings.  The  wing-veins  of 
Homalomyia  run  without  a  sharp  bend  to  the  margin  of  the  wing. 
This  creature  is  really  not  even  a  muscid;  it  belongs  to  the  Anthomy- 
idee.     It  breeds  in  waste  organic  matter  such  as  manure. 

Muscina  is  a  muscid  ge- 
nus. Our  species  may  be 
recognized  by  the  fact 
that  they  are  black  flies 
and  not  shining;  the  me- 
dian stripe  on  the  thorax 
is  light,  the  fourth  longi- 
tudinal vein  is  only  slightly 
bent  and  the  first  posterior 
cell  is  scarcely  contracted 
at  the  margin;  the  hind 
end  of  the  thorax  may  be 
reddish.  M.  stabulans  has 
the  legs  and  palpi  more  or  less  yellowish,  while  those  of  M.  assimilis 
are  wholly  black.  The  larvse  feed  on  excrement  and  a  variety  of 
decaying  substances  including  fungi  and  vegetables. 

Pollenia  rudis  is  known  as  the  "cluster  fly"  from  the  habit  which 
the  adults  have  of  congregating  in  masses,  especially  about  the  ceilings 
of  rooms,  when  they  are  looking  for  a  place  in  which  to  hibernate. 
When  mashed,  these  flies  are  very  greasy  and  have  an  odor  which 
has  been  described  by  some  as  like  honey  and  by  others  as  "very 
disagreeable."  They  breed,  as  parasites,  in  earthworms.  The  thorax 
has  no  distinct  stripes  and  is  usually  covered  with  a  yellowish  "dust"; 
the  space  between  the  eyes  is  white,  the  fourth  longitudinal  vein  is 
sharply  bent. 

The  genus  Lucilia  includes  the  "green-  and  blue-bottle  flies." 
Both  the  thorax  and  abdomen  are  bright  and  metallic.  This  descrip- 
tion would  apply  also  to  certain  other  Muscidse,  but  it  has  not  been 


Fig.  5.    THE  LITTLE  HOUSE  FLY 
{Homalomyia  canicularis) 


10 


INSECTS  AND  DISEASE 


l,.V.Col«n»^. 

M6. 


Fig.  6.    THE  STABLE  FLY  (Muscina  stabidans) 


Fig.  7.    THE  BLUE-BOTTLE  FLY  (Lucilia  c&sar) 
11 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

shown  that  the  "bottles"  are  instrumental  in  transmitting  diseases  and 
a  further  diagnosis  would  require  going  into  details  which  would  be 
out  of  place  here.  The  larvse  feed  chiefly  on  carrion  but  those  of 
L.  ccesar  occur  also  in  garbage  and  excrement. 

These  notes  on  various  Muscidse  (in  a  broad  sense)  and  an 
Anthomyid  have  been  given  for  the  purpose  of  introducing  the  table 
given  below.1  It  will  be  seen  from  this  table  that  the  only  fly 
which  is  very  abundant  on  human  excrement  and  also  in  dining 
rooms  is  Musca  domestica.  This  is  the  principal  reason  why  this  fly 
is  so  dangerous. 

Flies  found  in  Dining  Rooms 


Very                  ..         .                 Moderately                0 
..        J                 Abundant            ..               f                Rare 
Abundant                                          Abundant 

Very 
Abundant 

Musca 
domestica 

Borborus 
equinus 

Abundant 

Muscina         Sarcophaga 
stabulans         sarracenicz 

Ophyra 
leucostoma 

Pseudopyrelia 
cornicina 

Myospila 
meditabunda 

Moderately 
Abundant 

Homalomyia 
canicularis 

Lucilia 
ccesar 

Rare 

Drosophila          Pollen  ia 
ampelophila            nidi's 

Stomoxys         Calliphora 
calcitrans     erythrocephala 

1Reprint  from  the  Field  Book  of  Insects  (G.  P.  Putnam's  Sons),  by  Frank  E. 
Lutz.  It  may  not  be  out  of  place  to  say  that  this  book  gives  further  details,  which  can- 
not he  included  here,  concerning  the  identification  and  habits  of  other  insects  which  are 
troublesome  but  not  actually  dangerous. 


12 


INSECTS  AND  DISEASE 


BITING  FLIES 

Stomoxys  calcitrans.  If  ordinary  house  flies  seem  to  be  adding 
to  their  other  vices  by  biting,  it  is  a  case  of  mistaken  identification; 
the  culprits  are  almost  certainly  the  Stomoxys  calcitrans,  the  "biting 
stable  fly."  Its  proboscis  is  long,  slender,  and  pointed,  not  fleshy  and 
blunt  as  is  that  of  Musca  domestica  (page  5).  The  name,  stable  fly,  is 
not  very  appropriate,  as  this  fly  is  neither  the  most  abundant  fly 
about  stables,  as  a  rule,  nor  does  it  breed  chiefly  about  stables  unless 
a  quantity  of  wet,  fermenting  hay  or  straw  be  present.  Piles  of 
lawn-cuttings  or  of  weeds  furnish  more  Stomoxys  than  do  ordinary 
stables.  Adults  are  more  frequently  found  about  buildings  in  damp 
weather  and  just  before  a  storm  than  at  other  times,  for  which  reason 
the  saying  has  arisen  that  the  biting  of  flies  is  a  sign  of  a  storm.  The 
best  method  of  control  is  self-evident — do  away  with  the  breeding 
places  either  by  destroying  the  material,  covering  it  so  that  flies 
do  not  have  access  to  it,  or  drying  it  so  that  the  larva?  cannot  live. 


Fig.  8.    THE  BITING  STABLE  FLY  {Stomoxys  calcitrans) 

The  most  conspicuous  biting  flies  in  the  Northeastern  United  States 
belong  to  the  Tabanidse  and  are  variously  called  "horse  flies,"  "gad 
flies,"  and  "green-headed  flies."  The  head  is  large;  each  antenna 
has  three  joints,  the  last  being  somewhat  subdivided  into  from  four 


13 


AMERICAN  MUSEUM  GUIDE  EEAFEETS 


to  eight  parts;  the  eyes  are  large  and  usually  brightly  colored  when 
the  insect  is  alive;  the  proboscis  is  sometimes  as  long  as,  or  longer 
than,  the  body;  the  thorax  and  abdomen  bear  hairs  but  not  bristles; 
each  wing  has  two  submarginal  and  five  posterior  cells;  the  anal  cell 
is  usually  closed  but  not  far  before  the  border  of  the  wing;  the  mar- 
ginal vein  runs  entirely  around  the  wing.  The  larva?  are  aquatic, 
or  semi-aquatic,  and  predacious.  They  taper  at  both  ends  and  each 
of  the  eleven  segments  into  which  the  body  is  divided  bears  a  circlet 
of  small  spines.  The  adults  fly  by  day,  usually  being  found  in  warm 
sunny  places,  though  some  prefer  shady  woods.  Only  the  females 
bite;  both  sexes  feed  on  the  juices  of  plants  and  on  similar  substances. 
There  are  several  hundred  species  recorded  from  North  America. 

The  only  other  biting  Calypterate  which  we  have  in  the  North- 
east is  Hamatobia  serrata,  the  "Horn  fly."  It  is  less  than  half  the 
size  of  Stomoxys  calcitrans  and  the  palpi  are  nearly  as  long  as  the 
proboscis,  while  in  Stomoxys  they  are  much  shorter  than  the  proboscis. 

The  genus  Glossitia  includes  the  tsetse  flies;  it  is  found  only  in 
Africa  at  the  present  time,  although  it  formerly  occurred  in  America, 
as  is  proved  by  fossils  unearthed  in  Colorado.  The  tsetse  flies  are 
as  large  as,  or  larger  than,  Musca  domestica,  the  ordinary  house  fly; 
the  waist  is  constricted;  the  wings  are  crossed  when  at  rest;  the  fourth 
longitudinal  vein  bends  before  it  meets  the  very  oblique  anterior 
transverse  vein.  Both  sexes  bite,  usually  by  day,  but  also  at  night  if 
the  moon  be  bright.  The  larva?  almost  complete  their  development 
within  the  body  of  their  mother  and  are  then  laid  at  the  roots  of 
plants.  The  pupal  stage  lasts  from  six  to  eight  weeks.  Several 
species  have  been  described  and  their  habits  carefully  studied  but, 
owing  to  the  facts  that  the  larva?  are  carried  by  the  female  until  nearly 
or  quite  full-grown  and  that  the  adults  feed  on  the  blood  of  other 
animals  than  man,  control  methods  are  difficult. 

Certain  insects  are  not  real  transmitters  of  disease  but  are  them- 
selves its  inciting  agents.  There  are,  for  instance,  dipterous  larva?, 
"maggots,"  which  occur  by  accident  or  as  a  part  of  their  normal  life- 
history  in  the  human  body.  Such  an  occurrence  is  called  myiasis. 
The  most  important  species  in  this  connection  is  the  "screw-worm," 
Chrysomyia  macellaria.  It  is  a  blow  fly  which  has  been  classed  with 
the  Muscida?  and  also  with  the  Sarcophagida?.  The  adult  fly  is 
nearly,  or  quite,  half  an  inch  long;  metallic  green;  with  three  longi- 

14 


INSECTS  AND  DISEASE 


tudinal  dark  stripes  on  the  thorax;  its  head  is  reddish  to  yellowish 
brown;  its  wing  venation  is  similar  to  that  of  Musca  domestica. 
Several  hundred  eggs  (sometimes  the  eggs  hatch  before  they  are  laid 
and  then  living  larva?  are  deposited)  are  placed  on  carrion  or  in 
wounds  or  sores  in  living  animals.  In  the  case  of  man,  the  eggs  are 
usually  laid  in  the  nostrils  of  those  suffering  from  nasal  catarrh. 
The  yellowish-white  larva  has  rings  of  bristle-like  structures  on  the 
segments,  which  give  it  the  appearance  of  a  screw.  If  it  is  not  re- 
moved from  the  nostril,  it  may  work  in,  causing  an  abscess  and  even 
death.  Blow  flies  of  the  genus  Calliphora  (Muscida?  with  metallic 
colored  abdomen  but  dull  colored  thorax;  fourth  longitudinal  vein 
sharply  bent;  distal  third  of  antennal  bristle  bearing  some  hairs; 
cheeks  unicolorous)  sometimes  lay  their  eggs  on  cold  meat,  espec- 
ially pork,  and  the  larva?  are  then  taken  into  the  stomachs  of  careless 
eaters.  Usually  not  much  harm  is  done.  The  same  is  true  of 
Lucilia  (see  page  10).  The  (Estrida?  are  closely  related  to  the 
Muscida?  but  the  adults  have  rudimentary  mouth-parts.  They  are 
the  bot  flies,  and  certain  species  do  great  damage  to  stock.  In  trop- 
ical America  human  beings  are  parasitized  by  the  (Estrid  Dermatobia 
hominis,  and  possibly  other  species.  The  larva?  live  underneath  the 
skin  of  various  parts  of  the  body.  William  B.  Herms,  in  his  useful 
Medical  and  Veterinary  Entomology  (Macmillan  Medical  Co.,  New 
York),  gives  a  key  to  the  larva?  ordinarily  involved  in  myiasis. 


15 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


THE  FILTH  FLY  AND  DISEASE 

Musca  domestica  is  not  only  a  pest  but  a  serious  menace  to  health 
on  account  of  the  likelihood  that  it  may  carry  filth  from  the  unsavory 
places  which  it  frequents  to  food.  The  foot  of  the  fly  is  tipped  with 
claws  and  soft  pads  on  which  there  is  ample  room  for  great  numbers 
of  microbes  to  be  transplanted;  and,  as  a  matter  of  fact,  if  a  fly  be 
allowed  to  walk  over  the  surface  of  a  properly  prepared  bacterial 
culture  plate,  the  path  over  which  it  travels  is  marked  by  numerous 


THE  FOOT  OF  THE  FLY 


Fig.  9 


colonies  of  bacteria,  each  developed  from  a  single  germ  planted 
there  by  the  foot  of  the  insect.  Even  more  serious,  perhaps,  is  the 
danger  that  disease  germs  ingested  by  a  fly  from  privy  contents,  or 
other  infected  material,  may  be  voided  in  its  excrement  (fly  specks) 
or  in  small  droplets  which  are  regurgitated  by  the  insect.  Experi- 
ments have  shown  that  many  kinds  of  disease  germs  may  pass 
through  the  intestines  of  the  fly  and  be  discharged  in  its  excrement  in 
:in  active  and  virulent  state. 


16 


INSECTS  AND  DISEASE 


The  spoiling  of  foods  may  obviously  be  hastened  by  ordinary 
putrefactive  germs  introduced  in  such  ways  and,  if  the  fly  has  been 
reeding  upon  human  discharges  (tuberculous  sputum  for  example,  or 
the  contents  of  an  outside  closet  used  by  an  incipient  typhoid  case) 
specific  human  diseases  may  easily  result. 


Fig.  10.    BACTERIAL  COLONIES  DEVELOPED  ON  AN  AGAR 

PLATE  FROM  GERMS  PLANTED  BY  THE  FEET 

OF  A  FLY  WHICH  WALKED  OVER  IT 

The  number  of  microbes  actually  carried  by  flies  varies  greatly 
with  the  general  amount  of  filth  in  their  surroundings.  Studies  made 
by  the  New  York  Association  for  Improving  the  Condition  of  the 
Poor  gave  an  average  of  13,986  bacteria  per  fly  (on  the  outer  surfaces 
of  its  body)  in  clean  localities,  against  1,106,017  in  dirty  surroundings. 
The  germs  of  typhoid  fever  and  Asiatic  cholera  have  been  isolated 
from  the  bodies  of  flies  caught  during  epidemics  of  these  diseases, 
and  we  have,  in  our  museum  of  living  bacteria  at  the  American 
Museum,  one  strain  of  typhoid  bacilli  isolated  in  this  way  in  the 
course  of  an  outbreak  in  New  Jersey. 


17 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


It  was  the  experience  of  the  American  troops  in  the  Spanish 
War  which  first  forcibly  called  attention  in  this  country  to  the  danger 
of  the  transmission  of  disease  by  flies.  About  one  out  of  five  of  our 
volunteer  soldiers  contracted  typhoid  during  the  campaign,  and  the 
investigators  who  studied  the  cause  of  this  disastrous  affair  concluded 
that  '"the  number  of  cases  of  typhoid  fever  in  the  different  camps 
varied  with  the  methods  of  disposing  of  the  excretions."  The 
typhoid  germs,  in  most  cases,  were  probably  spread  from  person  to 
person  by  more  or  less  direct  contact,  but  the  fly  undoubtedly  played  its 
part.  Doctors  Reed,  Vaughan  and  Shakespeare  pointed  out  in  their 
official  report  that  "flies  swarm  over  infected  fecal  matter  in  the  pits 
and  then  deposit  it  and  feed  upon  the  food  prepared  for  the  soldiers 
at  the  mess  tents.  In  some  instances,  where  lime  had  recently  been 
sprinkled  over  the  contents  of  the  pits,  flies  with  their  feet  whitened 
by  lime  were  seen  walking  over  the  food." 

The  investigators  also  point  out  that,  "Officers  whose  mess  tents 
were  protected  by  means  of  screens  suffered  proportionately  less 
from  typhoid  fever  than  did  those  whose  tents  were  not  so  pro- 
tected," and  again  that  "Typhoid  fever  gradually  disappeared  in  the 
fall  of  1898  with  the  approach  of  cold  weather  and  the  consequent 
disabling  of  the  flies." 

In  the  World  War  flies  have  constituted  a  grave  menace  to  the 
health  of  troops  operating  in  tropical  and  semitropical  regions.  On 
the  western  front  they  have  been  remarkably  well  controlled  by 
burning  manure  and  garbage  and  by  protecting  latrines.  At 
Gallipoli  and  in  Egypt,  however,  they  have  been  responsible  for  the 
spread  of  dysentery  and  many  other  parasitic  diseases  among  the 
French  and  English  troops. 

The  most  striking  evidence  in  regard  to  the  importance  of  the  fly 
as  a  carrier  of  disease  is,  perhaps,  that  furnished  by  the  experience 
of  Jacksonville,  Fla.  Ever  since  the  encampment  of  troops  at 
Jacksonville  in  1898  the  city  has  been  heavily  infected  with  typhoid 
fever.  No  reliable  data  are  available  before  1908,  but  the  typhoid 
death  rates  per  100,000  population  for  the  years  1908,  1909,  and  1910 
were  82,  75  and  106  respectively.  In  the  late  summer  of  1910  a  law 
was  passed  requiring  that  all  dry  closets  within  the  city  should  be 
rendered  fly-proof.  By  March,  1911,  about  75  per  cent,  of  the  closets 
had  been  brought  into  conformity  with  the  law  and  the  typhoid  rate 
for  the  year  dropped  to  63.  By  January,  1912,  practically  all  the  closets 
had  been  rendered  fly-proof  and  the  typhoid  rate  dropped  to  26. 

18 


fXSECTS  AND  DISEASE 


The  danger  of  transmission  of  disease  by  flies  increases  with  the 
extent  to  which  human  excreta  are  exposed  to  the  access  of  flies  and 
with  the  duration  of  the  warm  season,  which  favors  fly  breeding. 
Danger  is  not  confined,  however,  to  unsewered  rural  districts  or  to 
the  South.  The  Association  for  Improving  the  Condition  of  the  Poor 
in  New  York  City  made  a  careful  study  of  the  relation  between  flies 
and  infant  diarrhea  in  the  summer  of  1914.  Nearly  1000  infants 
were  carefully  observed,  half  of  them  being  in  ordinary  homes  and 
half  in  homes  where  special  efforts  were  made  to  protect  the  infant 
and  his  food  from  flies.  The  homes  studied  were  classified  accord- 
ing to  their  general  cleanliness  and  according  to  their  freedom  from 
flies.  In  the  homes  where  flies  were  abundant,  1.9  times  as  many 
infants  suffered  from  summer  diarrhea  as  in  the  homes  protected  from 
flies,  and  1.8  times  as  many  were  attacked  under  dirty  conditions  as  in 
the  clean  homes.  Where  both  factors  were  combined,  in  dirty  and 
fly-ridden  homes,  there  were  2.4  times  as  many  infants  who  suffered 
from  diarrhea  as  in  the  clean  and  fly-protected  tenements. 

PREVENTION  OF  FLY-BORNE  DISEASE 

The  practical  methods  of  controlling  the  spread  of  disease  by  flies 
fall  under  four  main  headings:  the  prevention  of  fly  breeding,  the 
destruction  of  adult  flies,  the  protection  of  human  discharges  from 
access  of  flies,  and  the  protection  of  food  by  screening  houses  and 
covering  the  food  itself. 

PREVENTION  OF  FLY  BREEDING 

The  usual  methods  employed  in  fighting  the  dangerous  Muscidae 
are  really  of  little  avail.  Sticky  fly-paper,  wire  flytraps,  and  poisons 
will  undoubtedly  kill  a  large  number  but  infinitely  more  are  breeding 
where  they  came  from.  Screening  our  windows  and  doors  will  un- 
doubtedly keep  many  out  but  it  is  not  pleasant  to  live  in  a  cage. 
Furthermore,  the  people  from  whom  we  buy  our  milk  and  other 
food-stuffs  may  not  be  so  careful.  The  only  thoroughgoing  method  ' 
is  to  stop  the  trouble  at  its  source  —  prevent  fly  breeding.  The 
adults  we  kill  cannot  thereafter  breed,  but  they  have  probably  done 
so  before  and  many  of  their  companions  are  sure  to  escape  altogether. 
If  we  could  do  away  with  the  breeding  places,  or  make  them  unfit 
for  fly  larvse,  or  keep  adult  flies  away  from  them,  the  thing  would  be 
done.  Nearly  all  the  books  and  lecturers  say  that  this  is  easy.  It  is 
well  to  be  optimistic  but  better  to  recognize  the  whole  truth.  It 
cannot  be  done  easily. 

19 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


If  anti-fly  campaigns  are  to  be  successful  your  neighbor  must 
keep  his  place  clean  too,  for  his  flies  are  just  as  apt  to  come  into  your 
house  as  his,  so  the  problem  becomes  one  for  the  whole  community. 
This  is  the  heart  of  the  matter.  A  few  earnest  individuals  or  well- 
meaning  Improvement  Societies,  by  themselves,  can  do  little  more 
than  cause  a  great  deal  of  trouble  and  very  little  good.  Laws  must 
be  made  and  enforced  so  that  the  ignorant  or  careless  may  not  make 
of  little  or  no  avail  the  work  of  the  intelligent  and  careful. 

Since  90  flies  out  of  every  100  are  probably  born  in  a  manure 
pile,  the  elimination  of  the  natural  breeding  places  of  the  fly  means, 
first  and  foremost,  the  proper  care  of  stable  manure.  Stables  should 
not  have  dirt  floors,  since  it  has  been  shown  that  the  ground  moistened 
by  animal  discharges  contains  many  larva?  and  pupa;.  Floors  should 
be  water-tight,  preferably  of  cement,  and  constructed  so  as  to  drain 
freely  into  a  sewer  or  covered  cement  pit.  In  wooden  floored  stables 
flies  should  be  excluded  from  the  ground  beneath  the  floor  boards. 
Openings  left  for  ventilation  should  be  screened  with  wire  and  no 
holes  should  be  bored  in  the  floor  for  drainage  of  urine. 


Fig.  1  1.     MODEL  SHOWING  A  GOOD  TYPE  OF  MANURE  BIN 

American  Museum  of  Natural  History  i 

The  surface  of  the  manure  is  being  sprinkled  with  a  chemical  to  prevent  fly  breeding. 

20 


INSECTS  AND  DISEASE 


It  has  generally  been  recommended  that  the  manure  itself  should 
be  kept  in  a  dark  vault  or  pit  from  which  flies  are  shut  out  by  screens, 
or  in  a  tight  covered  box.  The  health  officer  of  Asheville,  N.  C, 
where  an  unusually  successful  anti-fly  campaign  has  been  carried  out, 
believes  that  screening  of  manure  has  been  over-emphasized  and 
that  tightly  floored  boxes  and  thorough  and  complete  cleaning  up  of 
these  floors  at  frequent  intervals  are  the  main  desiderata.  He  points 
out  that  most  manure  already  contains  fly  maggots  when  placed  in 
the  bin  and  that  an  elaborately  screened  bin  is  hard  to  clean  so 
thoroughly  that  development  may  not  take  place  in  the  manure  left 
behind. 

A  method  of  storing  manure  which  is  specially  applicable  to 
military  camps  depends  on  the  fact  that  flies  cannot  breed  readily 
in  this  material  when  it  is  closely  packed.  A  rectangular  area  of 
ground  is  staked  off  and  the  manure  is  built  up  into  compact  heaps, 
the  sides  being  kept  straight  and  beaten  hard  with  shovels.  The  ad- 
jacent ground  is  also  beaten  hard  and  loose  straw  is  placed  in  small 
windrows  about  a  foot  from  the  edge.  The  absence  of  air  in 
the  interior  of  the  heap,  with  the  high  temperature  and  chemical 
products  due  to  bacterial  fermentation,  makes  the  manure  highly  un- 
favorable for  fly  development,  and  any  larva?  which  succeed  in  de- 
veloping in  the  surface  layer  will  pass  out  and  pupate  in  the  ring  of 
straw,  which  should  be  swept  up  every  two  or  three  days  and  burned. 

The  United  States  Bureau  of  Entomology  has  devoted  special 
attention  to  the  problem  of  chemical  treatment  of  manure  for  the 
purpose  of  poisoning  the  maggots  which  might  otherwise  be  bred 
therein.  Any  one  who  is  interested  in  the  control  of  this  insect  pest 
should  write  to  the  Bureau  of  Entomology,  Washington,  D.  C,  and 
to  the  Department  of  Agriculture  of  his  own  State,  for  the  latest 
recommendations  in  regard  to  this  method  of  treatment,  which  is 
constantly  being  improved  and  made  more  economical  and  efficient. 
The  following  suggestions  are  taken  from  Farmers'  Bulletin  851  of 
the  United  States  Department  of  Agriculture  and  represent  the  best 
procedures  available  in  1917. 

For  manure  or  other  refuse  not  to  be  used  as  a  fertilizer, 
powdered  borax  is  the  best  chemical  preventive  of  fly  breeding; 
.62  pound  per  8  bushels  of  manure,  or  about  1  pound  per  16  cubic 
feet,  will  destroy  90  per  cent,  of  the  larvse  present.  The  borax 
should  be  applied  in  solution,  or  water  should  be  sprinkled  on  after 
scattering  dry  borax  evenly  over  the  pile. 

21 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

Borax-treated  manure  in  large  amounts  may  injure  crops;  and, 
for  manure  which  is  to  be  used  on  the  land,  powdered  hellebore  may 
be  recommended.  A  water  extract  is  prepared  by  adding  ^  pound 
of  powder  to  every  10  gallons  of  water,  stirring  and  allowing  to  stand 
for  24  hours.  The  stock  mixture  thus  prepared  is  sprinkled  over  the 
manure  at  the  rate  of  10  gallons  to  every  8  bushels  (10  cubic  feet) 
of  manure.  Hellebore,  while  more  expensive  than  borax,  in  no 
way  injures  the  manure. 

A  third  alternative  has  been  suggested  by  the  Department  of 
Agriculture,  which,  while  showing  a  still  higher  first  cost,  involves 
the  use  of  substances  which  serve  directly  to  increase  the  fertilization 
value.  A  mixture  of  /4  pound  of  calcium  cyanamid  plus  x/i  pound 
of  acid  phosphate  to  each  bushel  of  manure  killed  98  per  cent,  of  the 
larva;  when  scattered  evenly  over  the  surface  and  wetted  with  water,  at 
the  same  time  adding  to  the  manure  the  valuable  elements  nitrogen 
and  phosphorus. 

"It  is  well  to  bear  in  mind  that  the  house  flies  breed  in  many  sub- 
stances other  than  horse  manure,  for  example,  in  pig  manure,  chicken 
manure,  ensilage,  moist  bran,  rotting  potatoes,  and  in  decaying 
matter  on  the  public  dumps  of  towns  and  cities,  and  it  is  necessary  to 
give  attention  to  all  such  accumulations  where  active  fermentation  is 
taking  place." 

A  highly  ingenious  method  of  preventing  breeding  of  flies  in 
manure  is  the  maggot  trap  devised  by  Dr.  E.  C.  Levy,  Health  Officer 
of  Richmond,  Va.  Its  use  is  described  by  Mr.  Hutchinson  of  the 
United  States  Bureau  of  Entomology  as  follows: 

"The  maggots  of  the  house  fly,  when  they  have  finished  breed- 
ing, show  a  distinct  tendency  to  migrate  and  will  crawl  away  from 
the  manure,  especially  if  it  is  moist,  in  search  of  a  comparatively  dry 
and  safe  place  to  pass  the  pupal  or  resting  stage.  Now,  if  the  manure 
is  placed  on  a  slatted  platform,  and  if  the  platform  stands  on  the 
floor  of  a  concrete  basin  containing  yi  inch  or  more  of  water,  the 
larvse  in  migrating  will  drop  into  the  water  and  be  drowned.  Each 
day  the  stable  cleanings  should  be  placed  on  the  platform  and  com- 
pactly heaped  and  well  moistened.  For  the  purpose  of  keeping  the 
manure  wet,  it  is  best  to  have  a  small  cistern  close  to  the  platform  and 
a  pump  so  placed  that  the  watering  of  the  manure  heap  is  easily  ac- 
complished. If  the  liquid  manure  from  the  stables  is  conducted  by 
drains  to  the  cistern,  the  valuable  plant  food  which  it  contains  will 
thus  be  added  to  the  manure  on  the  maggot  trap.     Experiments  have 

22 


LVSECTS  AND  DISEASE 


Fig.  12.    TRAP  FOR  THE  DESTRUCTION  OF  FLY  LARVAE 
'  Maggot  Trap) 


23 


AMERICA X  MUSEUM  GUIDE  LEAFLETS 

shown  that  the  maggot  trap  will  destroy  99  per  cent,  of  the  maggots 
developing  in  manure.  After  the  manure  has  been  standing  on 
the  maggot  trap  for  10  days  it  will  be  practically  free  from  maggots 
and  may  be  used  on  fields  or  gardens  or  stored  in  heaps  without 
likelihood  of  any  further  breeding  taking  place  in  it.  The  advantages 
of  the  maggot  trap  are  that  it  is  cheap,  requires  little  extra  labor  to 
operate  and  to  dispose  of  the  drowned  maggots,  and  it  does  not  lessen 
the  value  of  the  manure  but  rather  tends  to  preserve  it.  As  is  the 
case  with  all  other  methods,  the  use  of  the  maggot  trap  must  be  sup- 
plemented by  careful  attention  to  possible  breeding  places  other  than 
horse  manure." 

2.    Destruction  of  Adult  Flies 

Simple  and  effective  flytraps  may  be  used  to  some  advantage  in 
decreasing  the  number  of  flies.  Their  use  has  been  advocated  not 
only  because  of  their  immediate  results,  but  because  of  the  chance 
that  the  flies  may  be  caught  before  they  lay  their  first  batch  of  eggs, 
and  that  thus  the  possible  number  of  future  generations  will  be 
materially  reduced. 

Many  types  of  flytraps  are  on  the  market,  and  as  a  rule  the  larger 
ones  are  the  more  effective.  Anyone  with  a  few  tools,  however,  can 
construct  flytraps  for  a  small  part  of  the  price  of  the  ready-made  ones. 
A  trap  which  is  very  effective  in  catching  flies,  and  is  easily  made, 
durable,  and  cheap,  may  be  constructed  as  follows: 

"The  trap  consists  essentially  of  a  screen  cylinder  with  a  frame 
made  of  barrel  hoops,  in  the  bottom  of  which  is  inserted  a  screen 
cone.  The  height  of  the  cylinder  is  24  inches,  the  diameter  18  inches, 
and  the  cone  is  22  inches  high  and  18  inches  in  diameter  at  the  base. 
Material  necessary  for  this  trap  consists  of  four  new  or  second- 
hand barrel  hoops;  one  barrel  head;  four  laths;  10  feet  of  strips  1  to 
\Y-2,  inches  wide  by  Yz  inch  thick  (portions  of  old  boxes  will  suffice); 
61  linear  inches  of  12-  or  14-mesh  galvanized  screening  24  inches 
wide  for  the  sides  of  the  trap,  and  41  inches  of  screening  26  inches 
wide  for  the  cone  and  door;  an  ounce  of  carpet  tacks,  and  two  turn 
buttons,  which  may  be  made  of  wood."  The  cost  of  the  material  for 
this  trap  is  not  great,  and  in  many  cases  the  barrel  hoops,  barrel  head, 
laths  and  strips  can  be  obtained  without  expense. 

"In  constructing  the  trap,  two  of  the  hoops  are  bent  in  a  circle 
(18  inches  in  diameter  on  the  inside)  and  nailed  together,  the  ends 
being  trimmed  to  give  a  close  fit.    These  form  the  bottom  of  the  frame 

24 


INSECTS  AND  DISEASE 


(A),  and  the  other  two,  prepared  in  a  similar  way,  the  top  (B). 
The  top  (C)  of  the  trap  is  made  of  an  ordinary  barrel  head  with  the 
bevel  edge  sawed  off  sufficiently  to  cause  the  head  to  fit  closely  in 
the  hoops  and  allow  secure  nailing.     A  square,  10  inches  on  the  side, 


Fig.  13.    A  SIMPLE  FLYTRAP  (see  text) 

is  cut  out  of  the  center  of  the  top  to  form  a  door.  The  portions  of 
the  top  (barrel  head)  are  held  together  by  inch  strips  (D)  placed 
around  the  opening  one-half  inch  from  the  edge  to  form  a  jamb 
for  the  door.  The  door  consists  of  a  narrow  frame  (E)  covered 
with  screen  (F)  well  fitted  to  the  trap  and  held  in  place  (not  hinged) 
by  buttons  (G).  The  top  is  then  nailed  in  the  upper  hoops  and  the 
sides  (H)  formed  by  closely  tacking  screen  wire  on  the  outside  of  the 
hoops.  Four  laths  (I)  (or  light  strips)  are  nailed  to  the  hoops  on 
the  outside  of  the  trap  to  act  as  supports  between  the  hoops,  and 
the  ends  are  allowed  to  project  1  inch  at  the  bottom  to  form  legs  (J). 


25 


AMERICA X  MUSEUM  GUIDE  LEAFLETS 


The  cone  (K)  is  cut  from  the  screen  and  either  sewed  with  fine  wire 
or  soldered  where  the  edges  meet  at  (L).  The  apex  of  the  cone  is 
then  cut  off  to  give  an  aperture  (M)  1  inch  in  diameter.  It  is  then 
inserted  in  the  trap  and  closely  tacked  to  the  hoop  around  the  base." 

The  effectiveness  of  the  traps  will  depend  on  the  selection  of 
a  good  bait.  For  attracting  house  flies  beer  is  probably  the  best. 
It  loses  much  of  its  attractiveness  after  the  first  stages  of  fermentation 
are  over,  and  for  this  reason  it  should  be  renewed  every  day  or  two. 
Milk  is  also  a  good  bait.  Over-ripe  or  fermenting  bananas,  crushed 
and  placed  in  the  bait  pans,  give  good  results.  A  combination  of 
bananas  and  milk  is  more  attractive  than  either  used  separately.  A 
mixture  of  3  parts  water  and  1  part  cheap  molasses  is  very  attrac- 
tive after  it  has  been  allowed  to  ferment  for  a  day  or  two.  A  mixture 
of  equal  parts  of  brown  sugar  and  cheese  (or  curd  of  sour  milk), 
thoroughly  moistened,  give  good  results  after  it  has  been  allowed  to 
stand  for  three  or  four  days.  For  catching  blow  flies  and  other  meat- 
infesting  flies,  the  best  bait  is  the  mucous  membrane  from  the  lining 
of  the  intestines  of  hogs.     Ordinary  fish  or  meat  scraps  may  be  used. 

Fly  paper  is  sometimes  helpful,  particularly  the  long  slender 
roll  of  sticky  paper  hung  from  a  ceiling.  For  a  fly  poison,  Professor 
Phelps  of  the  United  States  Public  Health  Service  recommends  either 
formaldehyde  or  sodium  salicylate,  three  teaspoonfuls  of  the  40  per 
cent,  commercial  solution  of  formaldehyde,  or  the  same  amount  of 
powdered  sodium  salicylate  to  a  pint  of  water.  Nearly  fill  a  glass 
tumbler  with  the  solution,  place  over  this  a  piece  of  blotting  paper 
cut  to  circular  form  and  somewhat  larger  in  diameter  than  the  tum- 
bler, and  over  this  invert  a  saucer.  Invert  the  whole  device.  The 
blotting  paper  will  remain  in  the  proper  moist  condition  until  the 
entire  contents  of  the  tumbler  have  been  used  and  the  strength  of  the 
formaldehyde  solution  will  be  maintained.  A  little  sugar  sprinkled 
upon  the  paper  will  increase  the  attractiveness  of  the  poison  for  the 
flies.  Either  of  these  preparations  may  be  safely  used  where  there 
are  young  children,  although  the  addition  of  the  sugar  is  not  recom- 
mended in  such  cases. 

The  killing  of  flies  in  the  house  by  "swatters"  is  also  of  some 
value,  although  where  the  insects  are  abundant  the  majority  of  them 
should  be  eliminated  by  the  more  efficient  methods  of  trapping. 

Among  natural  enemies  which  help  to  destroy  flies  in  either  the 
larval  or  the  adult  state  are  hens,  swallows,  phoebes  and  other  birds, 
and  toads. 

26 


INSECTS  AND  DISEASE 


3.     Protection  of  Human  Discharges  from  Access  of  Flies 

The  measures  suggested  above  will  greatly  reduce  the  numbers 
of  flies  but,  as  a  rule,  will  not  do  away  with  them  entirely.  It  is, 
therefore,  always  essential  to  take  precautions  against  the  spread  of 
specific  human  diseases  by  guarding  intestinal  discharges  from  the 
access  of  flies.  Outside  closets,  where  they  cannot  be  replaced  by  a 
cesspool  or  sewer  system,  should  always  be  carefully  constructed  so 
as  to  exclude  insects,  all  openings  for  ventilation  screened,  and  cracks 
in  walls  or  openings  below  the  floor  level  tightly  closed.  In  the 
army,  the  construction  of  fly-proof  latrines  is  a  first  essential  of  camp 
sanitation. 

4.     Exclusion  of  Flies  from  Houses  and  from  Access  to  Food. 

Finally,  flies  should  be  excluded  from  dwellings  by  careful 
screening  of  doors  and  windows.  Screens  must  be  always  in  place 
and  must  fit  tightly.  In  particular,  the  kitchen  and  the  dining  room 
should  be  protected  in  this  way. 

The  covering  of  foods  in  stores  and  restaurants  is  one  of  the 
most  important  aspects  of  the  campaign  for  clean  and  pure  foods,  and 
it  is  wise  to  avoid  all  such  places  where  flies  are  abundant  and  food 
unprotected. 


27 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

THE  MOSQUITOES  AND  THEIR  ALLIES 

The  blood-sucking  habit,  and  the  modifications  of  mouth-parts 
necessary  to  such  a  habit,  are  to  be  found  in  several,  not  closely  re- 
lated, groups  of  the  two-winged  insects,  Diptera.  All  blood-suckers 
are  to  be  looked  on  with  suspicion,  because  of  the  possibility  that 
they  may  be  the  intermediate  hosts  of  disease-parasites.  Several  such 
insects  have  already  been  mentioned;  but  another  group  of  quite 
different  creatures  remains  to  be  discussed. 

If  a  moquito,  crane  fly,  or  some  similar  insect,  be  carefully  ex- 
amined, it  will  be  seen  that  the  antennas  ("feelers")  consist  of  not 
less  than  eight  joints,  rather  similar  one  to  another;  the  antennas  are 
usually  longer  than  the  thorax  (the  middle  part  of  the  body,  the  part 
which  bears  the  wings  and  legs);  the  anal  cell  (see  Fig.  14)  is  rarely 
narrowed  in  the  border  of  the  wing  and  the  discal  cell  is  usually 
absent.  These  are  distinguishing  characteristics  of  the  nematocerous 
Diptera  or  Orthorrhapha,  that  group  of  Diptera  to  which  mosquitoes, 
punkies,  black  flies,  and  blood-sucking  gnats  in  general  belong. 


Fig.  14.  STRUCTURAL  CHARACTERS  OF  THE  MOSQUITO 

"•    Antenna  b.    Thorax 

'••    Costal  vein  of  wing  d.    Anal  cell 

<■•    Tibia 

Of  the  Nematocera,  there  are  four  families  (Culicidse,  Psycho- 
didse,  Simuliidse,  and  Ceratopogonidse)  which  contain  blood-sucking 
species.  The  adults  of  the  first  two  of  these,  Culicida;  and  Psychodidee, 
unite  in  typically  having  the  following  characteristics:  at  least  nine 


28 


INSECTS  AND  DISEASE 


veins  extend  to  the  margin  of  each  wing;  the  top  of  the  thorax  does 
not  have  a  distinct  V-shaped  suture  near  the  middle;  the  costa  (Fig. 
14 1  continues  around  the  hind  margin  of  the  wing;  and  the  wing 
veins  bear  conspicuous,  scale-like  hairs.  The  Culicidse  (Mosquitoes) 
are  slender;  they  have  long,  slender,  usually  moderately  hairy  of 
scaly  legs;  their  tibia?  (the  second  large  joint  of  the  legs)  have  apical 
spurs;  the  wings  are  elongate  and  narrow.  The  Psychodidse  (Moth- 
flies)  are  small  and  robust;  their  legs  are  short  and  densely  hairy;  the 
tibia;  have  no  apical  spurs;  the  wings  are  short,  broadband  some- 
times pointed  apically.  The  Simuliida;  and  Ceratopogonida; 
have  more  than  four  distinct  longitudinal  veins  but  less  than  nine 
veins  extend  to  the  margin  of  each  wing,  and  the  wings  do  not  have 
a  network  of  fine  creases;  the  costal  vein  does  not  continue  beyond 
the  apex  of  the  wing;  and  there  are  no  ocelli  (small,  simple  eyes 
which,  when  present,  are  situated  between,  often  above,  the  con- 
spicuous  compound  eyes).  The  Simuliida;  (Black-flies,  etc.)  are 
usually  very  small  and  thick-set;  the  antenna;  are  shorter  than  the 
thorax;  each  antenna  is  composed  of  ten  or  eleven  closely  united 
segments,  not  plumose;  the  hind  pair  of  legs  are  more  or  less  dilated; 
the  anterior  veins  of  the  wings  are  stout,  the  posterior  ones  weak. 
The  Ceratopogonida;  (Punkies),  like  the  Chironomida;  with  which 
they  were  formerly  united  but  from  which  they  have  been  separated 
because  of  their  piercing  mouth-parts,  are  slender  delicate  gnats;  the 
antenna;  are  slender,  the  joints  more  or  less  constricted  and  some- 
times plumose;  the  femora  of  the  slender  legs  are  sometimes  thickened. 
General  notions  are  not  always  safe  guides  in  the  classification  of 
insects.  However,  our  general  notions  as  to  what  a  mosquito  is, 
combined  with  the  discussion  in  the  preceding  paragraph,  will  prob- 
ably suffice  to  enable  us  to  recognize  a  culicid.  No  male  of  any 
species  of  Culicida;  ever  "bites."  The  females  of  most  of  the  species 
with  which  we  come  in  contact  have  the  ability  and  desire  to  pierce 
the  human  skin  with  their  needle-like  mouths,  if  they  get  a  chance, 
and  to  suck  a  small  drop  of  blood.  If  this  were  all  they  did,  it 
would  be  bad  enough,  but,  when  they  pierce  the  skin,  they  inject  an 
irritating  substance,  saliva,  which  sometimes  "carries  with  it  the 
microscopic,  unicellular  animals  which  cause  malaria,  and  down  this 
minute,  microscopic  [salivary]  duct  has  flowed  the  fluid  which  has 
altered  the  fate  of  continents  and  played  a  conspicuous  part  in  the 
destruction  of  the  ancient  civilizations  of  Greece  and  Rome'' 
(Shipley). 


29 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


Fig.  15.     RESTING  POSTURE  OF  CULEX  (above) 
AND  ANOPHELES  (below) 


The  disease-bearing  and  rest-disturbing  habits  of  mosquitoes 
have  led  to  a  detailed  and  almost  feverish  study  of  their  taxonomy. 
Species  have  been  named  and  genera  erected  on  the  basis  of  char- 
acters which  are  very  difficult  for  the  non-professional  to  use. 
Formerly,  the  common  species  of  true  mosquitoes  inhabiting  the 
northern  part  of  the  United  States  were  divided  into  two  genera: 
\>iot>lieles  and  Culex.      As  Anofiheles  contains  the  malarial  mosquito 

30 


INSECTS  AND  DISEASE 


(or  mosquitoes;  it  is  the  more  important  in  the  present  connection, 
although  not  so  numerous  in  species  as  the  old,  inclusive,  Culex. 
Not  all  species  of  Anopheles  have  spotted  wings,  and  not  all  spotted 
winged  mosquitoes  are  Anopheles,  but,  for  practical  purposes  and 
especially  in  the  northeastern  United  States,  we  may  say  that 
mosquitoes  with  spots  on  their  wings  are  Anopheles  and  that  those 
with  plain  wings  are  something  else.  Furthermore,  the  adults  of 
Anopheles  are  given  to  holding  their  beaks  in  a  line  with  their  bodies 
while  Culex  points  the  beak  downward  at  an  angle  to  the  body-line. 
One  of  the  technical  points  used  in  identifying  adults  of  Anopheles 
concerns  the  relative  lengths  of  the  palpi  and  beak.  The  palpi  are 
delicate,  thread-like  organs,  one  on  each  side  of  the  beak.  In  the 
male  the  palpi  are  more  feathered  than  in  the  female;  this  is  even 
more  true  of  the  antenna?,  or  "feelers."  Both  sexes  of  Anopheles 
have  the  palpi  nearly,  or  quite,  as  long  as  the  beak;  the  females,  at 
least,  of  our  other  mosquitoes  have  the  palpi  relatively  short,  rarely 
exceeding  half  the  length  of  the  beak.  If  one  extends  the  three  first 
fingers,  the  middle  finger  may  be  taken  to  represent  the  mosquito's 
beak  and  the  other  two  fingers  the  pair  of  palpi  of  Anopheles.  If, 
now,  the  first  and  ring  fingers  be  bent  at  the  end  of  the  first  joint, 
the  three  fingers,  as  viewed  from  above,  may  serve  as  a  model  of 
the  relative  lengths  of  the  palpi  and  beak  of  the  female  Culex.  In 
applying  this  test,  be  careful  not  to  confuse  the  antenna;  with  the 
palpi. 


Fig.  16.    RESTING  POSTURE  OF  MOSQUITO  LARV/E; 
ANOPHELES  (left);  CULEX  fright)     ■ 

Mosquito  larva;  live  only  in  water  but  the  females  of  certain 
species  display  what  might  almost  be  called  foresight;  they  lay  their 
eggs  on  ground  which  will  later  become  covered  with  water,  as  on 
the  mud  of  low  places  along  a  salt-marsh.     The  most  familiar  mos- 


31 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

quito  eggs  are  those  of  the  rain-barrel  species — eggs  which  are  laid 
on  end,  side  by  side,  in  a  boat-shaped  mass  on  the  surface  of  the 
water  in  barrels,  tubs,  and  similar  places.  The  eggs  of  Anopheles  are 
laid  singly  but  frequently  they  float  close  to  each  other,  the  floating 
being  favored  by  special  structures  along  their  sides.  The  larva,  or 
"wriggler"  which  hatches  from  an  egg  of  Anopheles  has  a  very  short 
breathing  siphon  on  its  back  at  the  tail  end.  The  larva  is  lighter 
than  water;  when  feeding  or  at  rest,  it  floats  just  below  the  surface 
and  parallel  to  it;  when  disturbed  it  wriggles  vigorously  from  side  to 
side,  the  motion  sometimes  carrying  it  downward  but  more  frequently 
sideways.  When  at  the  surface,  the  end  of  the  breathing  siphon 
pierces  the  "surface  film,"  opens  up,  and  exposes  the  ends  of  the 
tracheae,  the  tubes  which  convey  air  to  all  parts  of  the  creature's  body. 
In  order  to  feed  on  the  microscopic  plants  and  other  organic  material 
floating  at  the  surface,  the  larva  twists  its  neck  until  its  mouth  is  on  a 
line  with  its  back.  While  there  are  other,  more  technical  characters, 
it  is  sufficient  to  say  that  a  mosquito  larva  which  has  a  short,  stubby 
breathing  siphon,  floats  parallel  with  the  surface  of  the  water,  and 
twists  its  head  to  feed  is  an  Anopheles.  The  Culex  larva  floats  at  an 
angle  with  the  surface  as  shown  in  Fig.  16,  and  has  a  relatively  long 
breathing  siphon. 

As  a  young  insect  feeds,  its  flesh  increases  but  its  skin  does  not 
stretch  sufficiently  to  accommodate  the  enlarging  body.  Therefore, 
the  old  skin  is  cast  from  time  to  time  and  a  new,  larger  skin  is 
formed.  Finally  there  comes  a  time,  as  in  the  case  of  such  insects 
as  moths  and  beetles,  which  like  the  Diptera  have  a  "complete 
metamorphosis,"  when  there  emerges  from  a  larval  skin  something 
which  is  neither  larva  nor  adult,  and  which  is  called  the  pupa.  The 
pupa  of  moths  is,  for  the  most  part,  immobile  and  frequently  enclosed 
in  a  protective  case,  the  "cocoon,"  which  is  spun  for  it  by  the  larva. 
The  pupa  of  mosquitoes  is  active,  but  not  so  active  as  a  larva,  and  it 
does  not  feed.  It  also  differs  from  the  larva  in  being  hunched  up 
instead  of  slender  and  in  having  a  pair  of  breathing  siphons  on  its 
thorax  (the  part  of  the  body  just  back  of  the  head)  instead  of  a  single 
siphon  on  the  tail.  The  pupa  of  Anopheles  closely  resembles  that  of 
Culex,  but  the  abdomen  is  more  sharply  curved  and  the  breathing 
siphons  are  more  dilated  at  the  top  and  relatively  shorter  than  in 
Culex.  The  adult  mosquito  finally  emerges  from  a  split  in  the  back 
of  the  cast  pupal  skin,  which  forms  a  miniature  boat  upon  which  the 

32 


INSECTS  AND  DISEASE 


adult  may  stand  while  stretching  itself  before  it  flies  away  to 
perpetuate  its  species,  perhaps  at  the  expense  of  ours.  Studies  on  a 
common  fresh-water  mosquito  {Culex  pipiens)  made  at  the  American 
Museum  showed  that  at  20°  C.  the  cycle  was  completed  in  19.6 
days,  at  25°  in  11.7  days,  and  at  30°  in  7.8  days. 

In  the  vicinity  of  New  York  City  there  are  three  fairly  common 
species  of  Anopheles:  punctipennis,  crucians,  and  what  was  formerly 
called  maculipennis,  more  recently  quadrimaculatus,  but  which  prob- 
ably should  be  called  guttulatus.  Remembering  Pope's  advice 
concerning  the  choice  between  the  old  and  the  new,  we  will  use  the 
name  quadrimaculatus. 

Anopheles  punctipennis  is  "a  medium  sized  dark  brown  mosquito 
with  the  upper  surface  of  the  thorax  dark  brown  at  the  sides  and 
with  several  narrow  lines  of  yellowish  gray  hairs  appearing  as  one 
broad  gray  stripe  in  the  center.  The  beak  and  legs  are  unbanded; 
the  wings  densely  clothed  with  black  and  yellow  scales,  two  large 
black  patches  and  two  smaller  ones  on  the  front  margin  especially 
conspicuous.  The  abdomen  is  dark  brown,  profusely  scattered  with 
yellowish  brown  hairs"  (Smith).  The  other  two  species  to  be 
mentioned  here  have  no  whitish  spot  on  the  front  margin  of  the 
wings. 

Anopheles  crucians  "is  brown,  not  quite  as  dark  as  punctipennis, 
with  the  thorax  striped  with  grayish  scales,  the  wing  veins  clothed 
with  whitish  and  black  scales,  the  black  ones  especially  collected 
along  the  wing  margin"  (Smith).  The  hindmost  wing  vein  has 
three  black  spots  separated  by  two  yellowish-white  ones.  This 
mosquito  flies  earlier  in  the  evening  and  later  in  the  morning  than 
either  punctipennis  or  quadrimaculatus,  and  has,  for  this  reason,  been 
called  the  Daylight  Anopheles. 

Anopheles  quadrimaculatus  may  be  recognized  by  the  four  small 
dark  spots  on  each  of  its  yellowish  wings.  It  is  the  species  usually 
thought  of  in  connection  with  malaria  in  this  country  and  it  has  been 
observed  to  breed  in  brackish  water  as  well  as  fresh. 

Little  need  be  said  concerning  the  other  mosquitoes  of  northern 
regions,  in  connection  with  disease.  They  are  troublesome  on 
account  of  their  biting  habit,  and  for  the  same  reason  they  are  to  be 
looked  on  with  suspicion  since  they  may  be  the  unknown  carriers 
of  some  disease.  The  females  have  relatively  short  palpi  and  the 
larva;  relatively  long  breathing  siphons.      In  the  South,  however, 

33 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

there  are  certain  very  important  species.  Culex  quinquefasciatus, 
also  known  as  fatigans,  extends  as  far  north  as  Washington  and  St. 
Louis,  its  larva?  replacing  the  northern  pipiens  in  the  rain-barrels. 
In  both  species  the  eggs  are  laid  in  boat-shaped  masses  floating  on 
the  surface  of  the  water.  The  wings  of  both  species  are  clear  and 
both  species  have  white  cross-bands  on  the  abdomen;  these  abdominal 
bands  are  joined  to  lateral  spots  in  pipiens  but  separated  from  the 
lateral  spots  in  quinquefasciatus. 

Aedes  calopus,  formerly  called  Stegomyia  fasciata,  the  Yellow- 
fever  Mosquito,  is  frequently  carried  by  vessels  into  temperate  regions 
but  it  has  not  succeeded  in  establishing  itself  there.  The  adult  flies 
by  day  instead  of  by  night.  Aedes  is  a  genus  which  is  separated  from 
Culex  by  characters  rather  difficult  for  the  layman  to  make  out. 
Some  of  our  common  salt-marsh  mosquitoes  are  now  put  in  this 
genus.  The  following  list  of  characters  will  probably  differentiate 
calopus  from  anything  with  which  it  is  likely  to  be  confused;  the 
claws  on  the  front  and  middle  feet  of  the  female  are  toothed;  the 
joints  of  the  black  feet  are  white-ringed,  but  at  the  bases  only;  the 
beak  of  the  female  is  not  white-ringed;  the  thorax  is  not  markedly 
paler  than  the  abdomen  and  bears  silvery-white  lines  in  the  pattern 
of  a  lyre,  but  no  median  white  line;  the  abdomen  has  distinct, 
segmental  white  bands  which  are  continuous  across  the  abdomen;  the 
wing-scales  are  narrow  and  mostly  brown. 

Howard  and  others,  in  their  report  on  mosquitoes  published  by 
the  Carnegie  Institution,  say  concerning  calopus:  "Under  natural 
conditions  the  eggs  are  laid  singly  in  small  irregular  groups  some 

distance   above    the    margin   of   the   water The  larva?  live  in 

accumulations  of  water  in  artificial  receptacles.  From  being  origi- 
nally a  tree-hole-inhabiting  species,  it  is  now  wholly  domesticated, 
and  its  larva  inhabits  artificial  accumulations  of  water  either  within 
houses  or  in  the  vicinity  of  human  habitations.  Occasionally  the 
larva?  occur  in  holes  in  trees,  but  always  in  proximity  to  habitations. 
Goeldi  has  found  the  larva?  in  water  held  by  bromeliads,  presumably 
near  houses,  and  by  the  still  folded  leaves  of  banana  plants.  In  the 
tropics  the  earthen  jars  in  which  drinking  water  is  kept  within 
dwellings  are  favorite  breeding-places;  the  larva?  have  the  habit  of 
keeping  to  the  bottom,  and,  as  these  jars  are  never  emptied,  their 
presence  is  not  even  suspected.  Water  may  be  poured  from  the 
small  earthen  bottles  used  in  hotels  in  the  tropics,  and,  unless  the 
bottle    is   quickly  and  completely  emptied,   the   larva?  will  remain 

34 


INSECTS  AND  DISEASE 


behind.  Holy-water  founts  in  churches  are  a  favorite  breeding-place. 
Out  of  doors  the  larvse  occur  in  tanks,  barrels,  rain-barrels,  rain- 
troughs  and  discarded  bottles  and  tins.     The  larvae,  when  suspended 

from  the  surface  film,  hang  nearly  perpendicular Unlike  many 

other  mosquitoes  they  (the  adult  females)  emit  no  sound  when  about 
to  bite.  The  male  likewise  persecutes  man  and  this  has  led  to  a 
widely  quoted  statement  of  Ficalbi  that  it  sucks  blood;  however,  it 
does  not  pierce  the  skin  but  laps  sweat  from  the  surface  and  in  this 
way  causes  some  irritation." 

Several  other  families  of  nematocerous  Diptera  should  be  briefly 
mentioned  on  account  of  their  blood-sucking  habits. 

Psychodidae.  Some  of  the  characteristics  of  this  family  were 
given  on  page  29.  The  most  common — possibly  the  only — genus 
found  in  the  vicinity  of  New  York  City  is  Psychoda.  Its  larvse  live 
in  decaying  vegetable  matter,  exuding  sap,  cow  dung,  and  other 
moist  excrementitious  matter.  The  small,  moth-like  adults  run  well 
but  fly  weakly.  They  feed  largely  on  nectar  and  rarely,  if  ever, 
"bite"  animals,  although  they  may  sip  fluids  from  wounds.  In  the 
tropics  there  is  a  genus,  Phlebotomus,  in  which  the  species  have  the 
proboscis  rather  elongated  and  these  do  pierce  the  skin  of  man  and 
other  animals  for  the  purpose  of  sucking  blood.  Some  of  these 
species  are  believed  to  be  instrumental  in  the  transmission  of  disease. 

Simuliidae.  See  page  29  for  some  of  the  characteristics  of  the 
family.  The  species  have  received  various  common  names  including 
"buffalo  gnats,"  "black-flies,"  "sand-flies"  and  "turkey  gnats." 
The  principal  genus  is  Simulium  and,  although  there  are  not  many 
species,  individuals  sometimes  occur  in  countless  hordes.  The  larvse 
live  in  running  water,  usually  where  the  current  is  swiftest.  There 
the  larvae  sit  on  their  tails  catching  for  food  the  organic  matter  which 
the  stream  floats  to  them.  They  are  often  so  numerous  that  the 
object  on  which  they  are  gathered  seems  to  be  covered  with  moss. 
Unfortunately,  the  bite  of  the  adult  is  not  in  proportion  to  its  small 
size  and  when  hundreds  of  bites  are  received  in  one  day  it  is  easy  to 
believe  the  reports  of  deaths  of  both  cattle  and  human  beings  from 
the  bites  alone.  In  addition  to  this,  they  have  been  suggested  as 
possible  carriers  of  anthrax  to  cattle  and  of  pellagra  to  man. 

The  Ceratopogonidse  were  mentioned  on  page  29  because  of 
their  biting  habits;  they  have  not,  as  yet,  been  connected  with  any 
disease.  The  species  of  Culicoides  are  the  blood-sucking  "punkies" 
or  "  no-see-ums."     The  larvse  are  aquatic. 

35 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

MOSQUITOES  AND  MALARIA 

Few  diseases  have,  until  recent  times,  seemed  more  mysterious 
than  malaria.  This  malady  was  defined  in  Quain's  Standard 
Dictionary  of  Medicine  as  late  as  1894  as  "an  earth-born  poison, 
generated  in  soils,  the  energies  of  which  are  not  expended  in  the 
growth  and  sustenance  of  healthy  cultivated  vegetation.  By  almost 
universal  consent  this  poison  is  the  cause  of  all  the  types  of  inter- 
mittent and  remittent  fevers,  commonly  called  malarial,  and  of  the 
degeneration  of  the  blood  and  tissues  resulting  from  long  residence 
in  places  where  this  poison  is  generated." 

"  Malaria,"  the  Encyclopedia  continues,  "has  generally  been 
said  to  be  the  product  of  heat,  moisture  and  vegetable  decomposition. 
The  terms  marsh  miasm,  and  paludal  fevers,  long  employed  to 
distinguish  the  poison  and  the  fevers  to  which  it  gives  rise,  mark  the 
almost  universal  belief  that  the  air  of  marshes  alone  is  endowed  with 
the  power  of  generating  them.  That  low,  moist,  and  warm  localities 
are  generally  noted  as  malarious,  is  indisputable.  Marshes  are  not, 
as  a  rule,  dangerous  when  abundantly  covered  with  water;  it  is  when 
the  water  level  is  lowered,  and  the  saturated  soil  is  exposed  to  the 
drying  influence  of  a  high  temperature  and  the  direct  rays  of  the 
sun,  that  this  poison  is  evolved  in  abundance.  The  production  of 
malaria  on  a  great  scale  in  this  way  was  seen  in  the  district  of 
Burdwan,  in  Bengal.  The  soil  is  alluvial,  but  dry;  and  until  within 
the  last  few  years,  Burdwan  was  more  salubrius  than  the  central  or 
eastern  districts  of  the  lower  Gangetic  delta.  The  drainage  of  the 
district  became  obstructed  by  the  silting  up  of  its  natural  and  artificial 
outlets,  the  result  being  a  water-logged  condition  of  the  soil,  the 
development  of  malaria,  and  an  alarming  increase  in  the  death-rate. 

"Malaria  is,  however,  generated  under  conditions  apparently 
widely  different  from  the  above.  When  the  British  Army  under 
Wellington  was  operating  in  Estremadura,  the  country  was  so  arid 
and  dry  for  want  of  rain,  that  the  rivers  and  small  streams  were 
reduced  to  mere  lines  of  widely  detached  pools;  yet  it  was  assailed 
by  a  remittent  fever  of  such  a  destructive  malignity  that,  says 
Ferguson,  who  records  the  fact,  'the  enemy  and  all  Europe  believed 
that  the  British  host  was  extirpated.' ' 

Again  "The  disturbance  of  soil  that  has  long  been  fallow  is  often 
followed,  both  in  hot  and  temperate  climates,  by  the  evolution  of 
malaria.  A  familiar  example  was  the  prevalence  of  intermittent 
fever  in  Paris  during  the  fortifications  of  the  same  city,  in  the  reign 
of  Louis  Philippe,  and  on  a  larger  scale  in  different  parts  of  France 
when  the  railways  were  in  process  of  construction." 

36 


INSECTS  AND  DISEASE 


It  had  been  noted  that  "malaria  is  freely  generated  at  the  bases 
of  mountain  ranges  in  tropical  climates,"  that  "temperature  exercises 
great  influence  over  its  development  and  activity,"  "many  places  can 
be  visited  with  impunity  in  winter  which  are  dangerous  in  summer 
and  autumn";  that  "malaria  drifts  along  plains  to  a  considerable 
distance  from  its  source,  when  aided  by  winds  sufficiently  strong  to 
propel,  but  not  to  dispel  it";  that  "under  the  influence  of  currents 
of  heated  air  it  can  ascend,  in  dangerous  concentration,  far  above  its 
source";  that  "a  belt  of  forest  interposed  between  any  malarial  place 
and  human  habitations  affords  considerable  protection." 

Could  anything  be  more  mysterious  than  this  picture?  Yet 
only  three  years  after  this  article  appeared  in  Quain's  Encyclopedia 
the  mystery  was  solved. 

The  germ  of  malaria,  a  Protozoan  parasite  which  destroys  the 
red  cells  of  the  blood,  had  been  first  seen  by  a  French  surgeon, 
Laveran,  in  1880,  and  an  individual  observer  here  and  there  had 
suggested  a  possible  connection  between  malaria  and  mosquitoes. 
In  1883  an  American,  A.  F.  A.  King,  had  urged  with  special  force 
the  hypothesis  that  "the  mosquito  is  the  real  source  of  the  disease 
rather  than  the  inhalation  or  cutaneous  absorption  of  a  marsh 
vapor." 

It  was  only  in  the  early  nineties,  however,  that  the  proof  of  this 
assumption  was  at  last  furnished.  Patrick  Manson  and  Ronald  Ross, 
two  English  physicians,  at  that  time  began  serious  work  on  the 
mosquito  theory  and  in  1897  Ross  discovered  the  germ  of  bird 
malaria  in  the  stomach  of  the  mosquito.  The  Italians,  Grassi  and 
Bignami,  first  demonstrated  the  germ  of  human  malaria  in  the  body 
of  the  mosquito  in  1898  and  in  1900  Sambon  and  Low  showed  that 
it  was  possible  to  remain  immune  from  disease  in  the  most  malarious 
region  of  the  Roman  Campagna  if  protected  against  mosquitoes 
while  Dr.  Manson's  son  and  another  volunteer  were  inoculated 
with  malaria  in  England  by  the  bites  of  infected  mosquitoes  shipped 
alive  from  Italy. 

The  malaria  germ  is  an  example  of  a  parasite  which  requires 
two  different  hosts  in  which  to  complete  its  life  history.  Asexual 
cycles  are  completed  in  the  blood  of  man  at  regular  intervals  of  48 
or  72  hours,  the  recurrent  period  of  chill  and  fever  corresponding  to 
the  time  at  which  new  generations  are  set  free  in  the  blood  stream. 
The  complete  development  of  the  parasite,  however,  must  be  accom- 
plished in  the  stomach  of  a  mosquito  belonging  to  the  genus  Anopheles. 

37 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

When  one  of  these  mosquitoes  sucks  the  blood  of  a  malaria  patient 
it  draws  in  the  germ  which  passes  through  its  sexual  stage  in  the 
body  of  the  mosquito;  and  after  a  period  often  or  twelve  days  a  new 
generation  of  germs  find  their  way  into  the  salivary  glands  of  the 
mosquito,  where  they  lie  ready  to  infect  any  new  victim  who  may 
be  bitten  by  the  insect. 

The  control  of  mosquito  breeding,  then,  at  last  offered  definite 
hope  of  checking  this  disease  which  had  laid  so  heavy  a  burden 
upon  many  populous  countries  and  some  of  the  most  fertile  regions 
of  the  earth. 

Celli  estimated  that  malaria  caused  two  million  cases  of  disease 
and  15,000  deaths  a  year  in  Italy.  We  have  no  adequate  statistics  of 
its  ravages  in  the  southern  United  States,  although  the  importance 
of  the  problem  has  recently  been  forcibly  set  forth  in  an  admirable 
monograph  by  Mr.  F.  L.  Hoffman. 

A  careful  study  made  in  Alabama  in  1911  revealed  70,000  cases 
and  770  deaths  in  that  one  state  and  that  one  year.  Certain  counties 
in  southern  Missouri  have  experienced  death  rates  from  malaria  of 
over  100,  and  in  one  instance  nearly  300  per  100,000  population. 
Howard  estimates  the  money  loss  due  to  this  disease  in  the  United 
States  at  $100,000,000  a  year. 

During  the  past  summer  (1917)  malaria  was  the  second  largest 
cause  of  sickness  among  our  American  troops  in  mobilization 
camps. 


38 


INSECTS  AND  DISEASE 


CONTROL  OF  MOSQUITO- BORNE  DISEASE 

The  control  of  mosquito-borne  disease  involves  five  principal 
measures:  (1)  the  elimination  of  mosquito-breeding  places,  (2)  the 
destruction  of  mosquito  larva?  in  accumulations  of  water  which  can- 


Fig.  17.    MOSQUITO-BREEDING  NEW  JERSEY  MARSHLAND 
BEFORE  DRAINAGE 


Fig.  18.    SAME  AREA  SHOWN  iN  Fig.  17  AFTER  DRAINAGE 

not  be  removed,  (3)  the  destruction  of  adults,  (4)  the  protection  of 
human  beings  from  access  of  mosquitoes,  and  (5)  immunization  and 
treatment  by  the  use  of  quinine. 


39 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

Those  who  would  control  injurious  insects  should  use  a  combina- 
tion of  common  sense  and  knowledge  of  the  insects'  habits.  It 
should  not  be  necessary  to  mention  the  second  factor,  for  common 
sense  would  point  out  the  necessity  of  such  knowledge,  except  that 
so  many  otherwise  sensible  people  pick  up  a  smattering  of  entomol- 
ogy and  straightway  feel  competent  to  handle  the  complicated 
problems  presented  in  nature.  No  important  piece  of  work  should 
be  undertaken  without  expert  help.  On  the  other  hand,  mere 
knowledge  of  the  insect's  habits  is  not  sufficient,  as  has  been  shown 
by  some  utterly  impractical  methods  of  control  which  have  been 
suggested.  The  notes  which  have  been  given  here  on  the  habits  of 
mosquitoes  are  the  merest  outlines  and,  furthermore,  refer  chiefly  to 
those  species  which  seriously  trouble  man. 

The  most  fundamental  of  all  measures  ot  protection  is  the 
removal  of  the  original  source  of  all  mosquito  breeding,  accumula- 
tions of  stagnant  or  sluggishly  moving  water.  The  particular  measures 
adopted  must  vary  widely  with  the  type  of  mosquito  to  be  dealt 
with.  Along  the  shores  of  the  eastern  United  States,  for  example, 
the  salt-marsh  mosquito,  Culex  sollicitans,  furnishes  one  of  the  most 
important  problems  from  the  standpoint  of  nuisance,  although  this 
species  is  not  a  carrier  of  disease.  The  salt-marsh  areas  and  the 
neighboring  country  may  be  kept  reasonably  free  from  mosquitoes 
by  the  construction  of  comprehensive  systems  of  drainage  ditches 
which  keep  down  the  water  level  of  the  land  adjacent  and  are  them- 
selves flushed  out  by  the  tide.  Fresh  water  swamps  and  pools  where 
species  of  Anopheles  breed  may  be  treated  in  a  similar  way  or  in 
some  cases  may  more  economically  be  filled  in. 

In  dealing  with  the  common  malarial  mosquito  of  the  central 
United  States,  Anopheles  quadrimaculatus,  special  attention  must  be 
devoted  to  sluggish  streams  clogged  with  vegetable  growth.  If  such 
streams  are  straightened  and  cleared  of  weeds  their  rapid  flow  will 
no  longer  be  suitable  for  mosquito  breeding.  On  the  other  hand 
the  Culex  pipiens  and  A'edes  calopus  are  house  mosquitoes,  and  the 
most  important  measure  in  checking  these  insects  is  the  removal  of 
small  accumulations  of  stagnant  water  in  the  immediate  neighbor- 
hood of  habitations.  Such  inconspicuous  breeding  places  may 
produce  in  the  aggregate  great  numbers  of  mosquitoes;  and  every 
anti-mosquito  campaign  must  include  provision  for  systematic  house- 
to-house  inspection  if  it  is  to  be  successful. 

40 


INSECTS  AND  DISEASE 


Watch,  then,  for  unused  barrels,  tubs,  and  buckets;  roadside 
puddles;  hoof  prints,  ruts,  and  depressions  of  all  sorts;  barn-yard 
pools;  and  the  like.  In  cities,  special  attention  must  be  paid  to  the 
catch  basins  of  street  sewers  which  are  often  prolific  breeding  places. 
In  attempting  to  locate  wrigglers  in  such  places  water  should  be 
skimmed  (not  scooped)  from  the  margins  of  the  water  in  a  white- 
lined  cup  or  dipper.  Fountain-basins  should  contain  goldfish  since 
these  fish  are  voracious  feeders  on  mosquito  eggs  and  larva?,  or  the 
basins  should  be  emptied  and  thoroughly  dried  at  least  once  a  week 


Fig.  19.    OILING  A  MOSQUITO-BREEDING  SWAMP 

during  the  mosquito  season.  If  for  any  reason  a  pool  or  pond  cannot 
be  drained  there  are  two  principal  methods  of  preventing  it  from 
furnishing  the  neighborhood  with  mosquitoes:  the  surface  may  be 
covered  once  a  week  with  a  film  of  oil;  or  surface-vegetation  may 
be  removed,  the  sides  of  the  pool  made  sharp  and  steep,  and  the 
pool  well  stocked  with  goldfish.  The  first  method  is  not  entirely 
satisfactory  since  the  oil  must  be  renewed  so  often,  and  also  because 
an  oiled  pool  has  an  unpleasant  look  and  odor.  Kerosene  spreads 
well  but  evaporates  quickly:  crude  oil  lasts  longer   but   does   not 


41 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

spread  so  well  and  larvse  survive  between  the  patches  of  oil.  A 
mixture  of  about  equal  parts  of  kerosene  and  crude  oil  is  rather 
satisfactory.  It  should  be  applied  with  a  spray-pump.  Very  few,  if 
any,  of  the  numerous  patented  oils  are  worth  the  money.  "Larvicide" 
is  made  from  crude  carbolic  acid;  it  was  used  in  the  Panama  Canal 
work,  but  water  treated  with  it  is  poisonous  to  stock. 

Of  all  the  natural  enemies  of  mosquitoes,  fish  are  the  most 
important,  and  of  these  goldfish  are  the  most  dependable  and  easily 
secured,  but  small  ones  are  much  better  than  large  ones.  Top 
minnows,  such  as  species  of  Gambusia  and  Heterandria  (Fundulus) 
are  the  most  important  natural  enemies  of  mosquitoes.  It  is  true 
that  numerous  aquatic  insects  feed,  to  some  extent,  on  mosquito 
larva;  and  pupse,  but  they  are  rarely  numerous  enough  to  be  of  much 
value,  and  their  numbers  cannot  easily  be  increased  in  any  given 
pool.  The  usefulness  of  dragon-fly  larvse  and  adults  has  been 
greatly  exaggerated.  Tadpoles  are  vegetarians  and  do  not  make  a 
practice  of  eating  larvse. 

Since  Anopheles  larvse  frequently  live  in  water  which  flows 
rapidly  enough  to  wash  away  oil,  and  since  they  keep  close  to  the 
surface  of  the  water,  getting  above  leaves  of  aquatic  plants  where  fish 
do  not  see  them,  they  are  rather  difficult  to  control.  To  make 
matters  worse,  they  are  the  mosquitoes  which  we  are  particularly 
anxious  to  get  rid  of  since  they  are  the  only  ones  known  to  carry 
disease  in  the  North.  Cleaning  the  edges  of  streams  or  ponds, 
clearing  away  aquatic  vegetation,  and  keeping  a  good  stock  of  fish 
seem  to  be  the  only  feasible  methods  of  control,  although  in  small 
brooks  a  constant  supply  of  oil  may  be  furnished  from  a  specially 
designed  automatic  drip  can. 

In  regions  where  malaria  or  yellow  fever  or  any  other  mosquito- 
borne  disease  prevails,  such  measures  should  be  supplemented  by 
careful  exclusion  of  mosquitoes  by  the  use  of  window  screens  and  bed 
canopies,  and  special  precautions  should  be  taken  to  prevent  the 
biting  of  those  suffering  from  disease  by  mosquitoes  which  may  carry 
the  infection  to  others. 

The  application  of  these  various  methods  of  mosquito  control, 
with  thoroughness  and  over  sufficient  areas,  has  yielded  results  of  the 
most  definite  and  tangible  kind.  In  the  Italian  Campagna  the  pro- 
portion of  the  population  infected  with  malaria  was  reduced  from 
65%  to  12%  by  measures  directed  toward  the  eradication  of  the 
Anopheles  mosquito  and  was  then  brought  down  to  4%  by  the  free 
distribution  and  vigorous  advertisement  of  the  value  of  prophylactic 
doses  of  quinine.  Between  1902  and  1908  the  deaths  from  malaria 
in  the  whole  kingdom  of  Italy  fell  from  16,000  to  4,000. 

42 


INSECTS  AND  DISEASE 


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43 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


THE  CONQUEST  OF  YELLOW  FEVER 

The  discovery  of  the  mosquito  transmission  of  yellow  fever  is 
one  of  the  most  striking  and  dramatic  chapters  of  sanitary  science 
and  one  of  the  brightest  episodes  in  the  history  of  our  country. 

Between  the  years  1702  and  1800  this  terrible  disease  had 
appeared  in  the  United  States  thirty-five  times  and  between  1800 
and  1879  it  visited  the  country  every  year  with  two  exceptions.  In 
1793  a  tenth  of  the  population  of  Philadelphia  are  said  to  have 
perished  from  its  ravages. 

Mathew  Carey  writes  of  this  epidemic,  "the  consternation  of 
the  people  of  Philadelphia  at  this  period  was  carried  beyond    all 

bounds People  hastily  shifted  their  course  at  the  sight  of  a 

hearse  coming  towards  them.  Many  never  walked  on  the  foot-path 
but  went  into  the  middle  of  the  street,  to  avoid  being  infected  in 
passing  by  houses  wherein  people  had  died.  Acquaintances  and 
friends  avoided  each  other  in  the  streets  and  only  signified  their 
regard  by  a  cold  nod.  The  old  custom  of  shaking  hands  fell  into 
such  disuse  that  many  shrunk  back  with  affright  at  even  the  offer  of 
the  hand.  A  person  with  a  crepe,  or  any  appearance  of  mourning, 
was  shunned  like  a  viper.  And  many  valued  themselves  highly  on 
the  skill  and  address  with  which  they  got  to  the  windward  of  every 
person  they  met.  Indeed,  it  is  not  probable  that  London,  at  the 
last  stage  of  the  plague,  exhibited  stronger  marks  of  terror  than  were 
to  be  seen  in  Philadelphia  from  the  24th  or  25th  of  August  till  pretty 
late  in  September." 

The  Philadelphia  epidemic  was  the  occasion  of  a  vigorous 
discussion  as  to  the  contagiousness  or  non-contagiousness  of  the 
disease  in  which  the  eminent  Dr.  Benjamin  Rush  was  finally  con- 
verted from  the  latter  to  the  former  view.  For  over  a  century 
arguments  were  advanced  pro  and  con,  without  conclusive  result, 
and  as  late  as  1898  the  United  States  Marine  Hospital  Service 
summed  up  the  matter  as  follows:  "While  yellow  fever  is  a  com- 
municable disease,  it  is  not  contagious  in  the  ordinary  acceptation 
of  the  term,  but  is  spread  by  the  infection  of  places  and  articles  of 

bedding,  clothing  and  furniture One  has  not  to  contend  with 

an  organism  or  germ  which  may  be  taken  into  the  body  with  food 
or  drink,  but  with  an  almost  inexplicable  poison  so  insidious  in  its 
approach  and  entrance  that  no  trace  is  left  behind." 

44 


INSECTS  AND  DISEASE 


Fig.  21.   WALTER  REED 


Fig.  22.    JESSE  W.   LAZEAR 


Fig.  23.  JAMES  CARROLL  Fig.  24.  ARISTIDES  AGRAMONTE 


45 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

Two  years  later,  early  in  the  year  1900,  a  commission  of  army 
officers  was  appointed  to  study  the  disease  in  Havana  as  a  result  of  a 
number  of  cases  which  had  occurred  among  the  American  troops 
stationed  there.  The  Chairman  of  the  Commission  was  Dr.  Walter 
Reed,  and  his  associates  were  Dr.  James  Carroll,  Dr.  Jesse  W.  Lazear, 
and  Dr.  Aristides  Agramonte.  At  the  very  beginning,  the  investiga- 
tors turned  their  attention  to  the  mosquito  as  a  possible  agent  in  the 
transmission  of  the  disease.  Dr.  Carlos  J.  Finlay  of  Havana  had 
suggested  the  mosquito  theory  of  yellow  fever  very  convincingly 
in  1881,  though  without  experimental  proof,  and  the  discoveries 
of  Manson  and  Ross  and  Grassi  and  Bignami  had  recently 
demonstrated  a  similar  origin  for  malaria.  Reed  and  his  colleagues 
were  fortunate  in  thus  beginning  almost  at  once  with  a  correct 
hypothesis. 

The  lower  animals  do  not  suffer  from  yellow  fever,  so  that 
experiments  upon  human  subjects  were  essential.  In  the  words  of 
Dr.  Kelly's  life  of  Major  Reed,  "after  careful  consideration,  the 
Commission  reached  the  conclusion  that  the  results,  if  positive, 
would  be  of  sufficient  service  to  humanity  to  justify  the  procedure, 
provided,  of  course,  that  each  individual  subjected  to  experiment 
was  fully  informed  of  the  risks  he  ran,  and  gave  his  free  consent. 
The  members  of  the  Commision,  however,  agreed  that  it  was  their 
duty  to  run  the  risk  involved  themselves,  before  submitting  anyone 
else  to  it. " 

The  first  successful  experiment  was  made  with  Dr.  Carroll,  who 
allowed  himself  to  be  bitten  on  August  27  by  a  mosquito  which  had 
previously  bitten  four  yellow  fever  patients.  Four  days  later  he  was 
taken  sick  and  for  three  days  his  life  hung  in  the  balance.  Both  he 
and  Private  W.  H.  Dean,  the  second  case  produced  experimentally 
in  the  same  way,  recovered.  Dr.  Lazear,  however,  who  came  down 
with  the  disease,  not  as  a  result  of  the  experimental  inoculations  to 
which  he  also  had  submitted,  but  from  an  accidental  bite,  was  less 
fortunate  than  his  colleagues,  for  a  week  later  he  died,  after  several 
days  of  delirium  with  black  vomit. 

An  experimental  station,  named  "Camp  Lazear"  after  this  first 
martyred  member  of  the  party,  was  established  in  the  open  country; 
and  to  the  lasting  honor  of  the  United  States  Army,  volunteer  sub- 
jects for  the  experiments  from  among  the  troops  were  always  in 
excess  of  the  demand.       Private  John  R.   Kissinger  and  John  J. 

46 


INSECTS  AND  DISEASE 


Moran,  a  civilian  employee,  were  the  first  to  volunteer  "solely  in 
the  interest  of  humanity  and  the  cause  of  science,"  their  only 
stipulation  being  that  they  should  receive  no  pecuniary  reward. 

The  result  of  the  experiments  carried  out  at  Camp  Lazear 
proved  beyond  peradventure  that  yellow  fever  was  transmitted  by 
the  bite  of  a  certain  mosquito,  Aides  calopus,  and  in  no  other  way, 
for  non-immunes  who  lived  for  twenty  days  in  a  small,  ill-ventilated 
room,  in  which  were  piled  clothing  and  bedding,  loathsome  with 
the  discharges  of  yellow  fever  patients,  all  escaped  infection,  so  long 
as  they  were  protected  from  the  bites  of  mosquitoes. 

On  the  memorial  tablet  to  Lazear  in  the  Johns  Hopkins  Hos- 
pital is  the  inscription:  "With  more  than  the  courage  of  the  soldier, 
he  risked  and  lost  his  life  to  show  how  a  fearful  pestilence  is 
communicated,  and  how  its  ravages  may  be  prevented."  The  same 
risk  was  freely  taken  by  each  member  of  the  party  from  major  to 
private.  The  result  of  their  devotion  is  indicated  in  two  of  Reed's 
letters  to  his  wife,  "six  months  ago,  when  we  landed  on  this  island, 
absolutely  nothing   was   known    concerning   the   propagation    and 


Fig.  25. 


CAMP    LAZEAR   WHERE  THE  SECRETS  OF 
YELLOW   FEVER  WERE   REVEALED 


47 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

spread  of  yellow  fever — it  was  all  an  unfathomable  mystery — but 
today  the  curtain  has  been  drawn";  and  later  on  New  Year's  Eve — 
"only  ten  minutes  more  of  the  old  century  remain.  Here  have  I 
been  sitting  reading  that  most  wonderful  book,  'La  Roche  on 
Yellow  Fever,'  written  in  1853.  Forty -seven  years  later  it  has  been 
permitted  to  me  and  my  assistants  to  lift  the  impenetrable  veil  that 
has  surrounded  the  causation  of  this-  most  wonderful,  dreadful  pest 
of  humanity  and  to  put  it  on  a  rational  and  scientific  basis.  I  thank 
God  that  this  has  been  accomplished  during  the  latter  days  of  the 
old  century.  May  its  cure  be  brought  out  in  the  early  days  of  the 
new." 

The  practical  result  of  this  discovery  was  immediate  and  striking. 
In  the  half  century  or  so  for  which  we  have  records,  yellow  fever 
had  killed  an  average  of  750  persons  a  year  in  the  City  of  Havana. 
The  sanitary  reforms  introduced  by  the  American  army  of  occupa- 
tion which  produced  good  results  in  reducing  typhoid  and  smallpox 
had  been  powerless  against  yellow  fever  because  its  cause  was  as  yet 
a  mystery.  Following  immediately  on  the  experiments  at  Camp 
Lazear,  on  February  15,  1901,  a  campaign  was  begun  on  the  new 
lines  indicated,  by  screening  the  rooms  occupied  by  yellow  fever 
patients  and  destroying  all  mosquitoes  in  the  neighborhood.  As  a 
result  there  were  six  deaths  in  the  City  of  Havana  during  the  year  1901 
as  against  305  in  the  preceding  year,  and  although  sporadic  cases  have 
been  introduced  from  other  localities,  yellow  fever  has  never  again 
established  itself  in  Havana.  The  scourge  of  centuries  was  wiped 
out  in  a  single  year. 


48 


INSECTS  AND  DISEASE 


THE  SUCTORIA  OR  FLEAS 

The  Suctoria  or  fleas  are  small,  wingless,  jumping  insects  which 
are  strongly  compressed  sideways.  They  are  all  parasitic,  when 
adult,  on  warm-blooded  animals;  but  the  footless,  worm-like  larva? 
are  not.  Adults  of  both  sexes  have  piercing  mouth-parts  and  suck 
blood.  The  larva?,  however,  have  chewing  mouth-parts  and  feed 
on  more  solid  organic  material.  The  larva?  live  in  dust  and  refuse 
on  the  floor  or  ground  and  pupate  there,  usually  in  thin  silken 
cocoons. 

The  Dermatophilida?,  one  of  the  principal  families  of  Suctoria, 
have  the  segments  of  the  thorax  much  shortened  and  constricted, 
but  the  side-plates  of  the  metathorax  extend  over  two  or  three 
abdominal  segments;  the  third  antennal  joint  has  no  completely 
separated  false  joints;  and  the  fully  developed  female,  living  beneath 
the  skin  of  her  host  during  her  final  development,  has  a  greatly 
dilated  abdomen.  The  most  familiar  example  is  Dermatophilus 
penetrans,  the  "chigoe,"  "chique,"  "chigger,"  "jigger,"  or  "sand- 
flea."  The  fertilized  female  burrows  under  the  skin,  especially^ 
about  the  toes,  and  causes  a  nasty  ulcer.  The  eggs  which  she  lays  in 
the  ulcer,  or  the  larva?  which  hatch  from  them,  drop  to  the  ground 
for  further  development.  The  female  may  be  picked  or  squeezed 
out  of  the  ulcer  and  the  wound  should  then  be  carefully  treated  to 
clear  away  the  pus.  As  a  method  of  control — even  if  not  for  other 
reasons! — the  habitations  of  men  and  domesticated  animals  should 
be  cleaned  to  destroy  the  larva.  This  species  is  found  in  the  warmer 
parts  of  America  and  in  Africa.  Members  of  the  family  Pulicida?, 
on  the  other  hand,  do  not  have  the  thoracic  segments  much  con- 
stricted and  shortened  but  the  side  plates  of  the  metathorax  extend 
over  only  one  abdominal  segment;  the  third  antennal  joint  has  nine 
more  or  less  distinctly  separated  false  joints;  the  spines  on  the  hind 
tibiee  are  in  pairs,  are  few  in  number,  and  are  not  in  a  very  close-set 
row;  and  none  of  the  species  burrow  under  the  host's  skin.  In  the 
genus  Ctenocephalus  both  the  head  and  the  pronotum  (front  section 
of  the  thorax)  have  stout,  spine-like  bristles  (ctenidia);  the  last  tarsal 
joint  has  four  pairs  of  lateral  spines  and,  in  distinction  from  Neopsylla, 
the  eyes  are  distinct.  In  Ceratophyllus  the  head  has  no  ctenidia  but 
the  pronotum  does;  the  last  tarsal  joint  has  five  pairs  of  lateral  spines. 
In  Pulex  and  Xenopsylla  neither  the  head  nor  the  pronotum  has 
ctenidia.     The  distinction  between  these  two  genera  is  chiefly  based 

49 


AMERICAN  MUSEUM  GUIDE  LEAFLETS. 


on  internal  anatomy.  Ceratophyllus  fasciatus  is  the  rat  and  plague 
flea  of  temperate  regions.  It  feeds  on  rats,  mice,  skunks,  and  man. 
In  America,  it  seems  to  be  confined  to  California;  but  it  also  occurs 
abundantly  in  Europe.  Xenopsylla  cheopis  is  the  tropical  rat  and 
plague  flea.  Although  it  largely  confines  its  attentions  to  rats,  it 
.also,  unfortunately,  attacks  man.  The  cosmopolitan  human  flea 
{Pulex  irritans)  is  most  abundant  in  warm  regions,  and  attacks  rats, 
skunks,  and  domestic  animals  as  well  as  its  normal  prey,  man.  The 
cat  and  dog  fleas,  Ctenocephalus  canis  (female's  head  less  than  twice 
as  long  as  high)  respectively,  are  common  parasites. 


Fig.  26.    MODEL  OF  THE  FLEA  {Pulex  irritans) 

American  Museum  of  Natural  History 


50 


INSECTS  AND  DISEASE 


THE  BLACK  DEATH  AND  ITS  CONTROL 

Of  all  the  insect-borne  diseases,  the  one  that  has  proved  in  the 
past  most  deadly  to  mankind  is  bubonic  plague,  a  malady  closely 
bound  up  with  the  activities  of  the  insect  pests  which  have  just  been 
discussed.  We  have  records  of  the  ravages  of  this  disease  from  very 
early  times.  The  countries  of  the  Levant  have  been  centers  of  plague 
infection  for  3,000  years  as  a  result  of  their  unique  position  as  gate- 
ways between  the  East  and  the  West.  Plague  among  the  Philistines 
is  described  in  the  First  Book  of  Samuel,  the  golden  images  of 
tumors  and  of  mice,  prepared  as  sacrificial  offerings,  referring  clearly 
to  one  of  the  characteristic  symptoms  of  the  disease  and  to  its  preva- 
lence among  rodents. 


Fig.  27.    THE  PLAGUE  AT  EPIRUS.       P.  MIGNARD  ( 1  61  0-1  695) 

The  first  fully  recorded  pandemic  of  plague  broke  out  at 
Pelusium  in  Egypt  in  542  A.  D.  and  spread  by  way  of  the  principal 
trade  routes  of  the  time  into  Palestine  and  then  to  the  rest  of  the 
known  world.  Procopius  says  of  this  outbreak,  of  which  he  was  a  wit- 
ness "It  spared  neither  island  nor  cave  nor  mountain  top  where  man 
dwelt.  .  .  .  Many  houses  were  left  empty  and  it  came  to  pass  that  many 
from  want  of  relatives  and  servants  lay  unburied  for  several  days." 


51 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

The  second  pandemic  of  plague,  the  Black  Death  of  the  Middle 
Ages,  originated  in  Mesopotamia  about  the  middle  of  the  eleventh 
century.  In  the  track  of  travel  and  commerce,  particularly  on  the 
route  of  the  returning  crusaders,  it  quickly  spread  to  the  West  and 
North.  It  is  said  that  25,000,000  people,  one  fourth  of  the  population 
of  Europe,  perished  of  plague  during  the  fourteenth  century. 

A  third  pandemic  of  plague  which  is  still  going  on  at  the  present 
time  (1918)  broke  out  at  Yunnan  Fu  in  China  in  1871  and  attracted 
general  notice  when  it  reached  Hongkong  in  1894.    From  this  point 


Fig.  28.    MODEL  OF  CORNER  OF  RAT-INFESTED  DWELLING 

American  Museum  of  Natural  History 

the  disease  made  its  way  to  India  where  it  raged  unchecked  for  ten 
years  and  carried  off  6,000,000  people.  This  time,  however,  the 
world  invasion  of  the  Black  Death  was  to  be  met  by  a  new  defensive 
mechanism,  the  organized  force  of  scientific  research.  A  Japanese 
bacteriologist,  Yersin,  discovered  the  bacillus  of  plague  in  1894  and 
it  was  soon  proved  that  the  disease  from  which  rats  were  simultane- 
ously suffering  (as  they  had  done  in  the  days  of  Samuel)  was  the 
same  as  the  human  plague.  The  infection  may  be  more  or  less 
chronic  among  the  rodents,  persisting  among  them    for   years  as 


52 


INSECTS  AND  DISEASE 


tuberculosis  infection  does  in  man.  At  certain  times  and  under 
certain  conditions,  the  disease  becomes  more  virulent,  the  rats  die 
in  great  numbers,  and  infection  spreads  to  human  beings.  The 
agent  of  transmission  of  the  germ  from  rat  to  man  and  from  man  to 
man  remained  to  be  solved;  and  in  1897  and  succeeding  years 
evidence  accumulated  by  a  number  of  French,  English,  and  Russian 
investigators  began  to  point  more  and  more  strongly  toward  the  flea 


Fig.  29.    HABITAT   GROUP  OF  CALIFORNIA  GROUND  SQUIRRELS 

( Cilellus  variegatus  beecheyi) 
American  Museum  of  Natural  History 

as  the  intermediate  carrier  of  the  germ.  Finally  the  experiments  of 
the  Indian  Plague  Commission  rendered  this  practically  certain,  for 
they  showed  that  infection  did  not  spread  from  a  sick  to  a  well  rat 
even  when  in  intimate  contact  if  fleas  were  absent,  while  if  they 
were  present,  the  exposed  animals  quickly  came  down  with  the 
disease.  In  man  it  is  now  known  that  plague  may  at  times  (as  in 
Manchuria)  develop  a  peculiar  "pneumonic"  type  in  which    the 


53 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


germs  are  discharged  from  the  mouth  and  nose  as  in  the  case  of  a 
common  cold.  Pneumonic  plague,  therefore,  spreads  directly  from 
man  to  man  by  contact,  but  in  the  ordinary  or  "bubonic"  plague  the 
germs  are  not  discharged  in  any  of  the  excretions  of  the  body  and 
can  only  be  transmitted  by  the  flea.  In  northern  Asia  the  rodent 
host  of  the  plague  bacillus  is  the  Siberian  marmot  or  tarbagan, 
Arctomys  bobac,  and  the  first  human  victims  in  Manchuria  were 
trappers  and  dealers  in  marmot  skins.  In  California,  the  ground 
squirrel,  Citellus  variegatus  beecheyi,  is  infected,  and  the  United 
States  Public  Health  Service  up  to  September,  1913,  had  isolated 
plague  bacilli  from  1891  different  individuals.     A  number  of  human 


Fig.  30.    SHIP   EQUIPPED  WITH    GUARDS  ON    THE 

HAWSERS  TO   PREVENT   LANDING 

OF  INFECTED   RATS 

cases  in  California  were  traced  to  infection  from  these  animals.  The 
most  important  carriers  of  plague  germs,  however,  are  the  various 
rats,  the  black  rat  (Mm  rattus),  the  common  rat  of  the  middle  ages 
in  Europe,  the  brown  rat  [M.  norvegicus) ,  which  has  now  generally 
supplanted  the  smaller  and  less  ferocious  black  rat,  and  the  roof  rat 
(M.  alexandrinus)  which  has  established  itself  at  many  seaports. 

The  modern  campaign  against  plague  depends  mainly  upon  the 
control  of  the  rodent  host.  Human  cases  must  of  course  be  isolated 
but  the  great  essential  is  that  possibly  infected  rats  on  incoming  ships 
should  be  excluded  from  the  wharves  by  rat-guards  on  the  hawsers, 
and  rats  on  board  destroyed  by  fumigation.     In  seaports,  or  other 


54 


INSECTS  AND  DISEASE 


cities  where  plague  infection  is  likely  to  enter,  comprehensive  cam- 
paigns must  be  organized  for  the  removal  of  breeding  and  harborage 
places  of  rats  by  cleaning  up  rubbish,  for  the  starving  out  of  rats  by 
covering  garbage  and  eliminating  other  accumulations  of  food,  for 
trapping  and  shooting  and  poisoning  rats,  and  for  excluding  rats 
from  buildings  by  various  forms  of  ratproof  construction.  The 
natural  enemies  of  the  rat, — cats,  dogs,  and  ferrets,  skunks,  foxes, 
coyotes,  weasels,  minks,  hawks,  owls,  snakes,  and  alligators — are 
often  of  great  assistance  in  this  campaign. 


Fig.  31.    THE  SECOND  PANDEMIC  OF  PLAGUE. 
EXTENSION  OF  THE  DISEASE  BETWEEN  1200  AND  1450  A.  D. 

These  methods  of  rat  suppression  have  been  widely  successful 
in  their  application  to  the  control  of  bubonic  plague.  The  early 
history  of  the  present  pandemic  of  plague  is  precisely  like  that  of 
the  one  which  began  in  the  eleventh  century.  It  started  in  China, 
spread  to  Manchuria  in  one  direction,  and  killed  its  six  millions 
in  India.  Thence,  following  the  trade  routes  as  of  old,  plague 
infection  has  been  carried  to  seaports  all  over  the  world.     It   has 


55 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

passed  east  to  Melbourne,  Brisbane,  and  other  Australian  cities, 
north  to  Portugal  and  Scotland,  and  around  the  world  to  Brazil, 
Porto  Rico,  California,  and  New  Orleans.  We  are  actually  to-day 
in  the  midst  of  a  potential  world  pandemic  of  plague  like  that  of  the 
Middle  Ages;  but  our  knowledge  of  the  relation  of  the  rat  to  this 
disease  has  made  it  easy  to  prevent  general  spread  in  any  of  the 
countries  into  which  infection  has  been  introduced  outside  of  Asia. 


Fig.  32.     THE  THIRD  PANDEMIC  OF  PLAGUE. 
EXTENSION  OF  THE  DISEASE  BETWEEN  1897-1917. 


56 


INSECTS  AND  DISEASE 


Fig.  33.    MODEL  OF  THE  BODY  LOUSE  {Pediculus veslimenli) 

American  Museum  of  Natural  History 

LICE  AND  BED-BUGS 

Another  group  of  insects,  of  great  importance  in  connection 
with  disease,  is  the  family  of  Siphinculata  known  as  sucking  lice  or 
Pediculidse.  They  are  small,  more  or  less  flattened,  wingless  para- 
sites which  have  an  unjointed,  fleshy  beak  barely  reaching  the 
thorax.  The  five-jointed  antenna;  are  short;  the  tarsi  are  single- 
jointed,  forming  a  claw  at  the  end  of  the  tibiae;  the  eyes  are  well 
developed,  convex,  and  distinctly  pigmented.  The  eggs,  "nits,"  are 
fastened  on  the  hair  or  clothing  of  their  host.  The  metamorphosis 
is  slight  so  that  the  newly  hatched  young  closely  resemble  the  adults, 
and  there  is  no  resting,  pupal  stage.  Three  or  four  weeks  is  usually 
sufficient  time  for  these  creatures  to  reach  maturity  from  the  time 
the  egg  is  laid.     The  head-louse,  Pediculus  capitis,  is  more  common 


57 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

on  the  children  of  cleanly  families  than  is  generally  admitted  and  it 
is  almost  the  rule  among  the  less  cleanly,  The  former  get  it  from 
the  latter  by  contact,  by  using  the  same  comb  or  brush,  by  hanging 
the  hat  on  the  same  rack  in  school  and  in  other  ways.  The  body- 
louse  or  gray-back,  Pediculus  vestimenti  (or  corporis)  is  common 
where  men  gather  in  numbers  without  having,  or  using,  adequate 
facilities  for  cleanliness.  Cleanliness,  in  this  case,  refers  very  largely 
to  the  clothing,  as  this  species  lays  its  eggs  on  the  clothes  next  to  the 
skin  and  the  lice  themselves  spend  much  of  the  time  there.  The 
crab-louse,  Phthirius  inguinalis,  is  an  easily  recognized  species,  the 
common  name  being  appropriate.  It  infests  the  pubic  regions  and 
the  armpits  of  man.  Transmission  sometimes  occurs  by  way  of 
public  toilets. 

The  use  of  a  fine-toothed  comb  dipped  in  kerosene  is  an  effec- 
tive remedy  for  the  head-louse.  The  treatment  should  be  repeated 
twice  at  intervals  of  a  week.  For  body-lice,  the  clothing  should  be 
boiled,  steamed,  fumigated,  or  soaked  in  gasolene  or  benzine.  The 
irritation  caused  by  the  lice  may  be  relieved  by  a  lotion  of  one  half 
ounce  of  borax  to  a  pint  of  water.  In  dealing  with  these  lice  when 
there  is  danger  of  typhus  fever,  the  greatest  care  must  be  exercised 
to  prevent  their  spread.  The  face  and  the  head  should  be  shaved 
and  the  hair  burned.  A  liberal  use  of  kerosene  on  floors  and  about 
beds  is  recommended.  The  crab-louse  may  be  treated  in  the  same 
way  as  the  head-louse  but  mercurial  or  "blue"  ointment  is  often  used. 
The  salve  should  not  be  strongly  rubbed  in  or  used  directly  after  a 
warm  bath.  Vinegar  makes  the  eggs  of  the  lice  more  susceptible  to 
treatment. 

The  Bed-bug,  Cimex  lectularius,  an  insect  belonging  to  the 
Hemiptera,  has  received  many  more  or  less  descriptive  names  in 
addition  to  that  of  "bed-bug."  Some  of  them  are  "wall-louse," 
"red-coat,"  "mahogany  flat,"  "chinch,"  and  just  "bug."  Most 
people  are  familiar  with  this  insect,  whether  they  admit  it  or  not; 
others  usually  recognize  it,  by  instinct  or  by  its  reputation,  the  first 
time  they  meet  it.  There  is  a  mistaken  idea  that  the  flat,  dark- 
colored  insects  to  be  found  under  the  bark  of  decaying  logs,  and  the 
ones  that  occur  in  the  nests  of  swallows,  belong  to  the  species  under 
discussion.  Another  mistaken  notion  is  that  these  creatures  may 
become  "grandfathers  in  a  night."  The  eggs,  which  are  white  and 
oval  in  outline  with  a  rim  around  the  free  end  and  sculpturing  over 

58 


INSECTS  AND  DISEASE 


the  shell,  are  laid  in  cracks  and  crevices  in  beds  and  in  bedrooms. 
These  eggs  hatch  in  about  a  week.  The  young  resemble  the  adults, 
except  in  size,  and  there  is  no  pupal  stage.  After  molting  five  times, 
the  adult  stage  is  reached;  this  growth  takes  a  month  or  more, 
depending  on  temperature  conditions  and  the  amount  of  available 
food — the  blood  of  man,  and,  if  necessary,  of  other  warm-blooded 
animals  such  as  mice  and  poultry.  Bed-bugs  have  been  kept  alive 
and  active  for  a  year  in  a  tight  box  without  any  food  at  all.  Kero- 
sene, gasolene  and  benzine  are  effective  remedies,  if  forced  into  the 
crevices  where  the  bugs  hide  by  day.  The  treatment  should  be  ] 
repeated  at  intervals  of  about  a  week,  since  the  eggs  often  withstand 
this  treatment.  For  killing  them  on  a  large  scale,  there  is  nothing 
better  than  fumigation  with  hydrocyanic  acid  gas,  but  this  is  a  deadly 
poison  for  man  as  well  and  should  be  used  with  caution.  Those 
desirous  of  trying  it  should  write  to  their  State  Entomologist  or  to 
the  Bureau  of  Entomology,  United  States  Department  of  Agriculture, 
for  detailed  instructions. 

The  bed-bug  has  a  few  natural  enemies;  these  enemies  are, 
however,  not  greatly  to  be  preferred  to  the  bed-bug  itself.  "Kissing 
bug,"  of  much  newspaper  fame  a  few  years  ago,  is  a  name  applied  to 
several  insects  which  prey  upon  the  better  known  pest.  The  "masked 
bed-bug  hunter,"  Reduvius  personalis,  is  one  of  these.  The  "big 
bed-bug"  of  the  South,  Triantoma  (=Conorhifius)  sanguisuga,  is  much 
more  given  to  sucking  human  blood.  "It  is  about  an  inch  long; 
black,  marked  with  red  on  the  sides  of  the  prothorax,  at  the  base 
and  apex  of  the  front  wings,  and  at  the  sides  of  the  abdomen;  the 
head  is  long,  narrow,  cylindrical,  and  thickest  behind  the  eyes.  It  is 
said  that  the  effects  of  its  bite  may  last  for  nearly  a  year,  and  it  is 
probable  that  attacks  which  are  attributed  to  spiders  are  really  the 
work  of  this  insect.  Out-of-doors,  it  feeds  on  insects,  including 
grasshoppers  and  potato  beetles"  (Lutz,  "Field  Book  of  Insects"). 


59 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

TYPHUS  FEVER  AND  OTHER  DISEASES 
CARRIED  BY  THE  LOUSE 

Typhus  fever,  known  also  as  ship  fever,  camp  fever,  and  jail 
fever,  was  one  of  the  deadliest  of  the  diseases  of  the  Middle  Ages. 
Wherever  men  were  crowded  together  under  the  filthy  conditions 
which  surrounded  our  ancestors,  this  pestilence  raged.  In  sinister 
alliance  with  famine,  it  scourged  unhappy  Ireland  so  persistently  that 
it  was  known  as  "Irish  ague."  In  England  its  contagion  was  spread 
even  through  the  law-courts,  and  several  notable  outbreaks  among 
judges,  lawyers,  and  spectators  were  dubbed  the  "Black  Assizes" 
during  the  sixteenth  century.  In  Tuscany,  between  1550  and  1554, 
more  than  a  million  people  are  said  to  have  died  of  typhus. 

Professor  Curschmann  says  of  this  malady,  "between  1846  and 
1848  more  than  a  million  cases  of  typhus  occurred  in  England  and 
more  than  300,000  in  Ireland,  the  outbreak  starting  after  the  great 
famine  of  the  earlier  year.  In  every  century  typhus  fever  has  followed 
in  the  wake  of  armies.  During  the  Thirty  Years'  War  it  claimed 
more  victims  than  did  the  weapons  of  the  contestants.  It  was  the 
terror  of  the  Napoleonic  campaigns  and  decimated  the  French  Army, 
already  demoralized  physically  and  morally  by  the  terrible  retreat 
from  Moscow.  During  the  Crimean  War  it  decimated  both  the 
French  and  English  armies,  especially  the  former." 

Dr.  R.  Bruce  Low  describes  the  experience  of  France  with 
"camp  fever"  as  follows:  "When  the  French  in  1812  began  their 
historical  retreat  from  Moscow,  they  had  at  least  a  thousand  fever 
cases  among  them,  and  by  the  time  they  reached  Vilna  many  other 
attacks  had  occurred  with  numerous  deaths.  At  the  beginning  of 
December,  1812,  the  Russians  had  taken  30,000  French  prisoners, 
many  of  whom  were  ill  of  fever.  The  hospitals  at  Vilna  were  over- 
flowing with  the  sick,  who  suffered  greatly  from  cold  and  lack  of 
food.  Many  had  no  bed  or  bedding,  and  had  to  lie  on  rotten  straw, 
sometimes  side  by  side  with  the  dead.  Of  25,000  cases  sent  to  hos- 
pitals at  Vilna,  less  than  3,000  were  alive  at  the  end  of  January, 
1813.  From  the  troops  the  disease  in  many  instances  spread  to  the 
civil  population.  For  example,  in  the  fortified  town  of  Metz  no 
fewer  than  7,752  soldiers  of  the  garrison  died  of  typhus  during  1814, 
as  well  as  1,294  other  persons  in  the  civil  hospitals.  From  Metz  the 
infection  spread  to  the  neighboring  districts,  and  by  the  end  of  the 
year  no  fewer  than  10,329  deaths  from  typhus  had  occurred  in  the 

60 


INSECTS  AND  DISEASE 


Department  of  the  Moselle.  In  the  years  following  the  Napoleonic 
wars  the  disease  broke  out  from  time  to  time  in  different  parts  of  the 
country,  and  showed  special  incidence  among  the  inmates  of  convict 
prisons  and  local  jails.  In  1848  an  outbreak  of  typhus  was  started 
by  a  prisoner  at  Amiens,  who  infected  the  judge,  the  clerk  of  the 
court,  as  well  as  several  gendarmes  and  prisoners.  Similar  outbreaks 
occurred  at  Rheims,  Toulon  and  elsewhere  in  connection  with  civilian 
prisoners. 

"The  next  importation  of  typhus  fever  to  France  on  a  large 
scale  by  troops  occurred  on  the  return  of  the  French  military  forces 
from  the  Crimea,  where  they  had  suffered  severely  from  the  disease. 
It  is  reported  that  out  of  an  effective  force  of  120,000  men  at  least 
12,000  were  attacked  by  typhus  during  the  campaign,  and  that  half 
that  number  died. 

"Following  upon  the  return  of  the  troops,  outbreaks  of  typhus 
occurred  at  Marseilles,  Toulon,  Avignon,  Paris  and  elsewhere." 

Gradually  and  without  any  intelligently  directed  effort  to  control 
its  spread,  but  apparently  as  a  by-product  of  the  generally  improved 
sanitary  conditions  of  living,  typhus  fever  almost  disappeared  from 
civilized  countries.  "Typhoid"  fever,  named  from  its  resemblance 
to  the  more  deadly  typhus,  with  which  it  was  once  confused, 
remains  a  serious  menace,  but  typhus  was  almost  forgotten  in  west- 
ern Europe  until  war  broke  out  in  1914.  The  table  below  from 
Doctor  Bruce  Low  shows  how  the  deaths  from  this  disease  have 
decreased  in  England  and  Wales  and  in  Ireland. 

DEATHS  FROM  TYPHUS  FEVER  IN 

England  and  Wales  Ireland 

1869-1883                            23,702  11,544 

1884-1898                              2,249  4,703 

1899-1913                                 390  1,043 

In  certain  parts  of  the  world,  however,  where  sanitary  conditions 
remain  primitive,  typhus  has  held  its  own.  It  has  occasionally  found 
its  way  into  central  Europe  from  Poland  and  Galicia.  In  many  dis- 
tricts of  Mexico  it  has  long  been  a  serious  scourge;  and  an  infection, 
known  as  Brill's  disease,  which  occurs  in  New  York  City,  has  been 
shown  to  be  a  mild  form  of  typhus. 

Many  of  the  characteristics  of  typhus  fever  pointed  to  the  prob- 
ability of  an  insect  carrier,  and  suspicion  was  finally  fastened  upon 
the  louse  as  the  most  probable  culprit.      The  coincidence  between 

61 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


the  seasonal  and  geographical  distribution  of  the  disease  and  the 
insect,  in  particular,  seemed  significant,  high  temperature  apparently 
being  inimical  to  each.  At  last  in  1909  Nicolle,  Comte  and  Conseil 
succeeded  in  transmitting  typhus  fever  to  monkeys  by  the  bite  of  the 
body-louse.  This  result  was  confirmed  in  the  next  year  in  this 
country  by  Ricketts  and  Wilder;  and  Goldberger  and  Anderson 
showed  that  not  only  the  body  louse  {Pediculus  vestimenti)  but  also 
the  head  louse  {Pediculus  capitis)  may  transmit  the  specific  infection. 
As  an  illustration  of  the  danger  to  which  those  who  work  on  the 
insect-borne -diseases  are  exposed,  it  may  be  noted  that  one  of  this 
group  of  devoted  experimenters,  Howard  T.  Ricketts,  contracted  the 
disease  in  the  course  of  his  investigations  and  died,  almost  at  the 
outset  of  a  brilliantly  promising  career. 

With  the  outbreak  of  the  European  War  in  1914,  typhus  again 
came  into  public  notice  as  it  broke  out  in  malignant  form  on  the 
eastern  battle-front.  Its  effects  upon  the  course  of  campaigns  in  the 
Balkans  is  said  to  have  been  very  material;  but  the  French,  German 
and  Russian  armies  have  been  protected  against  its  ravages  by 
elaborate  provisions  for  the  destruction  of  lice  by  the  disinfection  of 
clothing  and  the  cleansing  and  disinfection  of  the  person,  particularly 
of  the  hair. 

The  body  louse  usually  conceals  itself  in  the  folds  of  the  clothing, 
depositing  its  eggs  along  the  seams  and  wrinkles.  A  female  may  de- 
posit nearly  300  eggs  which  hatch  in  3-4  days  and  reach  maturity  in 
15-18  days.  According  to  recent  studies  reported  in  English  medical 
journals,*  lice  are  able  to  live  without  food  for  2-6  days.  They  become 
rigid  with  cold  at  10°  F.  and  are  killed  in  2-6  hours  at  104°  F. 

Among  the  various  substances  which  have  been  employed  for  the 
destruction  of  lice,  the  most  efficient  appear  to  be  a  killing  powder 
composed  of  96  per  cent,  naphthalene,  2  per  cent,  creosote,  and  2 
per  cent,  iodoform,  and  an  ointment  known  as  vermijelli.  The 
soldier's  clothing  and  equipment  may  be  freed  from  lice  by  treatment 
in  either  dry  or  moist  heat  sterilizers  or  in  special  sterilizers  which 
make  use  of  the  simultaneous  effect  of  heat  and  formaldehyde 
in  vacuo.  Ironing  the  seams  of  garments  with  a  hot  iron  is  a  simple 
and  generally  effective  method.  Military  encampments  are  usually 
provided  with  special  stations  for  "delousing"  or  "depediculization," 

*An  excellent  review  of  recent  contributions  to  the  biology  of  the  louse  is  to  be 
found  in  "Household  and  Camp  Insects"  by  E.  P.  Felt,  Bull.  No.  194,  New  York  State 
Museum. 

62 


INSECTS  AND  DISEASE 


so  arranged  that  while  the  men  are  being  bathed  their  clothes  are 
simultaneously  freed  from  lice  by  one  of  the  methods  described 
above. 

In  addition  to  typhus,  a  form  of  relapsing  fever  is  not  uncom- 
monly spread  in  Russia  and  in  other  countries  of  southeastern  Europe 
by  the  bite  of  the  louse,  and  this  disease  has  offered  one  of  the  serious 
problems  of  army  sanitation  on  the  eastern  front. 


63 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

OTHER  DISEASES  TRANSMITTED  BY  ARTHROPODS 

In  addition  to  the  insect-borne  diseases  mentioned  above,  there 
are  many  other  diseases  of  tropical  countries,  which  are  transmitted  in 
a  similar  way  by  insects  or  by  their  relatives,  the  ticks.  Among  the 
most  important  of  these  are  sleeping  sickness  and  other  diseases 
caused  by  the  Protozoan  parasites  of  the  genus  Trypanosoma,  and 
transmitted  by  the  biting  flies  of  the  genus  Glossina,, and  certain 
forms  of  relapsing  fevers  and  similar  maladies,  caused  by  spirochetal 
parasites  transmitted  by  ticks. 


Fig.  34. 


DISTRIBUTION  OF  TEXAS  FEVER  OF  CATTLE  AND 
ROCKY  MOUNTAIN  TICK  FEVER 


The  ticks  are  not  insects  at  all  but  belong  to  the  Acarina  or  mites 
(see  page  4).  The  first  of  all  the  arthropod-borne  diseases  to  be 
definitely  worked  out  was  the  serious  cattle  plague,  known  in  our 
Southwestern  States  as  Texas  fever  and  in  Australia  as  redwater 
fever.  In  1889  Smith  and  Kilbourne  showed  that  the  causative  agent 
in  this  disease  was  a  Protozoan  parasite  (Babesia)  and  that  it  was  carried 
by  the  bite  of  a  tick,  Boophilus  annulatus.  Rocky  Mountain  spotted 
fever,  which  attacks  visitors  to  the  Bitterroot  Valley  and  other  areas 
in  the  Mountain  States,  is  spread  by  Dermacentor  an ders on i  and  other 
ticks.  The  most  terrible  of  tick-borne  diseases,  however,  are  the 
African  tick  fevers  or  relapsing  fevers  caused  by  different  species  of 
spirochetes. 


64 


INSECTS  AND  DISEASE 


Fig.  35.    THE  TSETSE  FLY  (Glossina  morsitans) 


Fig.  36.    TYPICAL  BREEDING  PLACE  OF  GLOSSINA 
ON  THE  BELGIAN  CONGO 


65 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 

The  head-  and  body-lice,  as  has  been  indicated,  are  the  agents 
in  the  transmission  of  typhus  fever  and  are  probably  active  in  the 
spread  of  European  relapsing  fever  as  well,  while  the  body-louse 
is  believed  to  play  a  part  in  the  transmission  of  the  special  form  of 
relapsing  fever  which  occurs  in  northern  Africa.  Bed-bugs  (Ci/nex) 
and  assassin-bugs  (Conorhinus)  are  probably  the  agents  in  dissemi- 
nating Opilacao  or  Chagas  fever  in  Brazil  and  Kala-azar  or  dum- 
dum fever  in  India  and  China. 

Of  the  trypanosome  diseases,  the  most  important  are  the  cattle 
disease  of  South  Africa,  Nagana,  carried  by  Glossina  mofsitans,  and 
the  sleeping  sickness  of  man.  It  is  estimated  that  between  1900  and 
1910  there  were  200,000  deaths  from  sleeping  sickness  in  the  Uganda 
Protectorate  alone.  The  particular  trypanosome  which  causes  this 
malady  is  carried  by  another  biting  fly,  Glossina  palpalis,  which  lives 
in  rather  sharply  limited  areas  of  dense  forest  and  undergrowth 
along  the  shores  of  lakes  or  rivers.  Clearing  the  jungle  for  a  hundred 
yards  along  the  water  courses  and  for  three  hundred  yards  about  all 
villages,  screening  of  houses,  protection  of  the  body  against  bites,  and 
the  isolation  of  the  sick  are  among  the  most  important  preventive 
measures  in  use  against  this  disease.  Surra,  a  cattle  disease  of  Asia, 
Malaysia,  and  the  Philippines,  somewhat  similar  to  Nagana,  is  a  try- 
panosome disease  spread  by  various  blood-sucking  flies,  while  sand 
flies  {Phlebotonius)  carry  the  unknown  germs  of  the  Pappatici  fever 
of  the  Mediterranean  and  Verruga  in  Peru.  The  suspicion  that 
epidemic  anterior  poliomyelitis  (infant  paralysis)  and  pellagra  are 
causally  connected  with  biting  flies  (Stomoxys,  Simulium)  has,  on  the 
other  hand,  not  been  substantiated. 

Among  the  mosquitoes,  besides  the  various  species  of  Anopheles, 
which  carry  the  germs  of  malaria,  and  the  Aedes,  which  transmits 
yellow  fever,  Culex  fatigans  spreads  the  virus  of  Dengue  fever,  and 
with  other  mosquitoes  is  the  agent  in  transmitting  the  microscopic 
worms  { Filar ia)  which  cause  elephantiasis  and  other  forms  of  filariasis. 


66 


INSECTS  AND  DISEASE 


r 


TRYPANOSOME 
Protozoan    which    causes   Sleeping 
Sickness  of  Central  Africa. 


Sporozoite  stage  of  the  germ  of  Malaria 


Bacillus  of  Bubonic  Plague 


LEISHMANIA 
Protozoan    parasite    which    c 
Indian  kala«azaror  dum-uum  feve 


SPJROCHAETA 
Parasite    which    causes    European 
Relapsing  Fever. 


Raund-worm  which  causes  tropical 
elephantiasis,  100  times  actual  length. 


Fig.  37.     MODELS  OF  BLOOD  PARASITES 

American  Museum  of  Natural  History 


67 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


Tabular  Review 

DISEASE 

West  African  Tick  Fever 
Rocky    Mountain    Spotted 
Fever 

Opila^ao  (or  Chagas  Fever) 

Texas  Fever  of  cattle 
Spirochaetosis  of  fowls 


Typhus  Fever 

Opilacao  (or  Chagas  Fever) 
of  Brazil 


European  Relapsing  Fever 

North  African  Relapsing 

Fever 
Kala-Azar  or  Dum-Dum 

Fever 


of  Principal  Insect 
parasite 

Spirochccta  duttoni 


Trypanosoma  cruzi 

Babesia  bigeminum 
Spirochccta  gallinarum 


Borne  Diseases 
carrier 

ACARINA  (mites) 
Omithodorus  moubata 

Dermacentor  andersoni 

and  other  ticks 
0.  moubata,  also  certain 

Hemiptera 
Boophilus  annulatus 
Argas  persicus 


Trypanosoma  cruzi 
Spirochczta  recicrrentis 

Spirochccta  berberi 
Leishmania  donovani 


HEMIPTERA  (bugs) 
Pediculus  capitis,  P. 

vestimenti 
Conorrhinus  megistus, 

Cimex  lectularius,  C. 

hemipterus,  also  certain 

ticks 
P.  capitis,  P.  vestimenti, 

also,  perhaps,  bedbugs 

Pediculus  vestimenti 

Conorrhinus  rubrofascia- 
tus  or  Cimex  hemipterus  (?) 


Bubonic  Plague 
Infantile  splenic 
leishmaniasis 


Bacillus  pes  lis 
Leishmania  infantum 


SIPHONAPTERA  (fleas) 
Xenopsylla  cheopis  and 

other  fleas 
Pulex  irritans  and  other 

fleas 


Sleeping  Sickness 
Nagana  disease  of  cattle 

Surra  of  cattle 
Verruga  peruviana 
Typhoid,    diarrheal  disease 
of  children,  etc. 


Trypanosoma  gawbiense 
Trypanosoma  brucei 

A  filterable  virus 


Various  bacteria 


DIPTERA  (flies) 
Glossina  palpal  is 
Glossina  morsitans  and 

other  flies 
Phlebotomies  papatasii 
Phlebotomus  verrucarum  (ft 

Masca  domes tica  (occa- 
sional accidental  carrier) 


Malaria — tertian 
quartan 
;esti\o-autumnal 

Yellow  Fever 

Filariasis 

Dengue 


Plasmodium  vivax 
P.  ma/aricr 
P.  falciparum 
A  filterable  virus 
Filaria  bancrofti 

A    filterable  virus 
63 


DIPTERA  (mosquitoes) 

Anopheles  maculipt •// //  is 
and  other  Anopheles  sp. 

A'edes  calopus 
Cu/exfatiga  us,  Anopheles 

nigerrimus  and  others 
Culex  fatigans 


INSECTS  AND  DISEASE 


THE  BUILDING  OF  THE  PANAMA  CANAL 
A  TRIUMPH  OVER  INSECT-BORNE  DISEASE 

By  far  the  most  serious  problem  which  confronted  the  United 
States  Government  in  the  attempt  to  cut  a  canal  across  the  Isthmus 
of  Panama  was  that  of  insect-borne  disease. 

The  Isthmus  was  first  visited  by  Columbus  on  his  third  voyage 
in  1498.  Permanent  settlements  were  established  shortly  thereafter 
by  Balboa,  and  the  conquest  of  Peru,  about  1530,  by  Pizarro  made 
the  Isthmus  a  center  of  unique  commercial  importance.  The  size 
and  magnificence  of  the  city  of  Old  Panama,  the  point  from  which 
Pizarro  sailed  forth,  which  Drake  half  a  century  later  reconnoitred 
from  both  its  land  and  water  sides,  and  the  stronghold,  which  the 
buccaneer  Morgan  captured,  sacked,  and  practically  destroyed  in 
1671,  has  been  greatly  exaggerated  by  the  earlier  chroniclers  and  by 
later  but  no  less  credulous  historians.  Yet  it  is  certain  that  an  enor- 
mous volume  of  travel  and  a  vast  quantity  of  gold  and  silver  bullion 
passed  across  the  Isthmus  between  Spain  and  her  imperial  colonies. 
The  result  of  this  constant  influx  of  non-immunes  in  a  region  admi- 
rably adapted  for  the  breeding  of  disease-carrying  insects  might  have 
been  anticipated.  The  Isthmus  became  "the  foremost  pest-hole"  of 
the  earth,  "infamous  for  its  fevers,  and  interesting  only  because  of 
the  variety  of  its  malarial  disorders  and  pestilences." 

The  failure  of  the  attempt  made  by  the  French  under  de  Lesseps 
to  build  an  Isthmian  Canal  ( 1880-1888)  was  due  to  various  causes  but 
most  of  all,  perhaps,  to  the  ravages  of  insect-borne  disease.  Nothing 
was  then  known  of  the  relation  of  mosquitoes  to  the  transmission  of 
malaria  and  yellow  fever.  The  hospitals  on  the  Isthmus  were 
unscreened,  and  potted  plants  stood  all  about  with  water  in  their 
saucers,  furnishing  an  ideal  breeding-place  for  A'edes  mosquitoes. 
Even  the  legs  of  the  beds  were  stood  in  cups  of  water  to  prevent  ants 
from  climbing  them.  It  is  no  wonder  that,  as  General  Gorgas  esti- 
mates, the  French  lost  about  one-third  of  their  white  working  force 
each  year  from  yellow  fever  alone. 

When  the  United  States  undertook  the  work,  the  epoch-making 
discoveries  of  Reed  and  his  associates  had  been  established,  and 
General  Gorgas,  fresh  from  his  successful  handling  of  the  sanitation 
of  Havana,  was-  detailed  as  sanitary  adviser  to  the  Isthmian  Canal 
Commission  in  1904.    It  is  difficult  to  believe  to-day  that  the  members 

69 


.  IMERICAN  MUSEUM  GUIDE  LEAFLETS 


of  the  Commission  were  at  first  quite  unconvinced  by  the  Havana 
investigations  and  the  practical  application  of  their  conclusions.  As 
the  non-immune  population  on  the  Isthmus  increased,  yellow  fever 
became  epidemic.  In  April,  1905,  several  of  the  higher  officials  were 
stricken,  and  panic  and  demoralization  threatened.  In  June,  .1905, 
the  Governor  and  Chief  Engineer  of  the  Commission  recommended 
that  General  Gorgas  and  other  adherents  of  the  "mosquito  theory" 
should  be  recalled  and  "men  with  more  practical  views"  appointed 
in  their  places.  President  Roosevelt,  however,  supported  the  sani- 
tary officers  with  his  accustomed  vigor,  and  Mr.  John  F.  Stevens, 
who  was  appointed  in  place  of  the  former  Chief  Engineer,  was  in 
cordial  sympathy  with  General  Gorgas'  plans.  The  work  now 
moved  forward  rapidly.  Mosquito  breeding  was  reduced  to  a  mini- 
mum by  clearing  away  brush  and  undergrowth,  by  draining  low  lands, 
and  by  the  use  of  larvicides.  Houses  were  screened,  and  in  partic- 
ular malaria  and  yellow  fever  patients  were  rigorously  isolated  from 
the  access  of  mosquitoes.  Quinine  was  provided,  and  its  systematic 
use  as  a  prophylactic  was  persistently  urged  upon  the  working  force. 

The  results  of  this  sanitary  work  were  as  strikingly  dramatic  as 
those  obtained  at  Havana.  In  1904  and  1905  there  were  35  deaths 
of  employees  from  yellow  fever  on  the  Isthmus,  but  by  the  end  of 
the  latter  year  the  situation  was  under  control.  In  May,  1906,  there 
was  one  case  at  Colon  and  there  has  not  been  a  single  case  on  the 
Isthmus  since  that  date. 

The  deaths  from  malaria  have  been  reduced  from  233  in  1906  to 
3  in  1916  with  a  larger  working  force,  and  the  table  of  case  rates 
below  quoted  from  Hoffman's  monograph  is  eloquent  of  the  results 
achieved. 


70 


CONQUEST  OF  MOSQUITO  BORNE  DISEASE  IN    PANAMA 


DEATH        RATE         FROM         YELLOW        FEVER 
PER  IOOOO  EMPLOYEES 


■ 


1905        1906        1907       1908       1909        I9IO         1911  1912         1913         I9M 


DEATH       RATE       FROM       MALARIA 


PER         IOOOO         EMPLOYEES 


Fig.  38. 
71 


AMERICAN  MUSEUM  GUIDE  LEAFLETS 


HOSPITAL  CASES  OF  MALARIA  AMONG  CANAL  ZONE 
EMPLOYEES  per  100  employed 


Year 

Case-rate 

1906 

81.9 

1907 

42.6 

1908 

28.2 

1909 

21.6 

1910 

18.7 

1911 

18.4 

Year 

Case-rate 

1912 

11.0 

1913 

7.6 

1914 

6.5 

1915 

4.5 

1916 

1.5 

General  Gorgas  estimates  that,  if  our  force  of  39,000  men  had 
suffered  as  the  French  suffered  from  disease,  there  would  have  been 
78,000  deaths  during  the  ten  years'  work  on  the  construction  of  the 
Canal.  There  were  actually  6,630  deaths,  indicating  a  saving  due  to 
efficient  modern  sanitation  of  over  70,000  lives. 

The  late  Charles  Francis  Adams  said  of  this  episode,  in  an 
Address  before  the  Massachusetts  Historical  Society  (Proceedings  of 
the  Massachusetts  Historical  Society  for  May,  1911),  "the  great  and 
most  startling  impression  left  on  me  by  what  I  saw  on  my  visit  to  the 
Zone  was  not  the  magnificent  ditch  itself,  nor  the  engineering  feats 
accomplished;  nor  yet  the  construction  work  in  progress.  These  are 
remarkable;  but  solely,  so  far  as  I  am  competent  to  judge,  because  of 
their  magnitude  and  concentratedness.  I  have  frequently  seen  steam 
shovels  at  work;  though  never  so  many,  nor  quite  so  busily,  as  now  in 
the  Culebra  Cut.  So  I  have  watched  pneumatic  drills  as  they  bored 
into  the  rock,  and  heard  the  detonation  of  the  dynamite;  though  at 
Panama  more  drills  would  be  working  at  once  and  in  closer  prox- 
imity than  I  ever  saw  before,  and  the  blasts  when  the  day's  work  was 
done  sounded  like  a  discharge  of  artillery  in  battle.  For  centuries 
all  civilized  nations  have  been  building  canals  and  dams,  though  the 
Gatun  Dam  breaks  the  record  for  bigness;  the  locks,  too,  at  Panama 
are  larger  and  longer,  and  more  elaborate  and  imposing  than  any 
yet  designed.  All  this  is  true;  and  yet  it  failed  deeply  to  impress  me. 
After  all,  it  was  a  mere  question  of  bigness — the  something  more  or 
something  less;  and,  as  a  result  of  organized  energy  and  systematic 
cooperation  of  forces  for  rapid  daily  accomplishment,  I  still  think 
the  construction  of  the  Pacific  railroads  fifty  years  ago  at  the  rate  of 
half  a  dozen  miles  a  day,  every  material,  even  water,  having  to  be 
hauled  to  the  moving  camp  which  constituted  the  advancing  front, — 


INSECTS  AND  DISEASE 


this  was  by  far  a  more  dramatic  display  than  anything  now  to  be 
seen  on  the  Isthmus.  Again,  the  Gatun  Dam  is  a  great  conception; 
but  as  such  the  recent  tunneling  of  the  Hudson  and  the  subterranean 
honeycombing  of  Manhattan  Island,  combined  with  the  bridging  of 
the  East  River,  impress  me  more.  Finally,  the  locks  at  the  entrance 
and  outlet  of  the  proposed  Chagres  Lake  are  imposing  structures; 
but  to  my  mind  the  terminal  stations  built,  or  now  in  process  of 
building,  in  the  heart  of  New  York  City,  are  more  imposing.  As  I 
have  said,  all  this  is  a  mere  question  of  degree,  and  time  out  of 
mind  the  world  has  been  building  roads  and  water-ways;  moreover, 
behind  this  particular  water-way  is  the  Treasury  of  the  United  States! 
But  when  it  comes  to  the  sanitation  which  made  all  that  is  now  going 
on  at  Panama  humanly  and  humanely  possible,— vanquishing  pesti- 
lence and,  while  harnessing  the  Chagres,  also  making  it  innocuous  to 
those  working  and  dwelling  on  its  banks,— this  is  new;  and  the  like 
of  it  the  world  had  not  before  seen." 


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